Why do states maintain this road but not that one?

[Alps]

Is NC 80 part of North Carolina's state route system?  It is not connected to any other highway except the Blue Ridge Parkway and dead ends at Mt. Mitchell.  It is not even signed its entire way.  It looks like any other spur of the Blue Ridge Parkway and it seems odd that it has an NC number given to it.

What? NC 80 connects to US 70 and NC 226A. http://www.vahighways.com/ncannex/route-log/nc080.html
You're thinking of NC 128. http://www.vahighways.com/ncannex/route-log/nc128.html

It was in 1991 I was there.  It was on a map I had then that I no longer have.  It might of been in error or I remember wrong.  Nonetheless, it is a state route designation that does not intersect with any other NC state maintained roads and it a spur of the BRP.

Dude, he said it was 128. So obviously your 80 is in error.

[bugo]

My home state, Arkansas, and my current state of residence, Oklahoma, are a study in contrasts.  Arkansas has far more state highway miles per square mile than Oklahoma does.  Many state highways in Arkansas would be county roads in Oklahoma, and many county roads in Oklahoma would be state maintained in Arkansas. 

[roadman65]

My home state, Arkansas, and my current state of residence, Oklahoma, are a study in contrasts.  Arkansas has far more state highway miles per square mile than Oklahoma does.  Many state highways in Arkansas would be county roads in Oklahoma, and many county roads in Oklahoma would be state maintained in Arkansas. 

What about NJ having more State Secondary (500 series numbers) than actual state designations?  It has all of its state routes (except in some urban areas and many miles of US 202 in North Jersey) all state maintained, and the 5xx are county routes.  If this was PA, all the secondary routes would be state maintained roads in addition to the other state routes.

Georgia is the same as well.  GA 122 between Lakeland and Waycross would be a county road in most states.
Of course if GA was NJ, US 202 would completely state maintained especially from NJ 53 in Morris Plains to the State Line at Suffern, NY.  There are no US designations in the Peach State without a companion state route, as many of us know.

[Laura]

Not in Maryland - the state (in the form of the State Highway Administration for "free" roads and the Maryland Transportation Authority for toll roads) maintains roads that are signposted with a route number, and sometimes maintains "dead end" roads that were left over when a highway was realigned (a lot of this was done in the 1950's through 1970's). 

...

The counties and the state will sometimes engineer a "swap," where some numbered roads are decommissioned to county roads, while others are "promoted" to state roads.

When I first read the topic title, my first thought was "because there is no rhyme or reason to why MD's SHA maintains the roads that it does".

The "dead-end" roads make sense to me, plus the roads that often dead end at the end of a neck of land. However, Maryland notoriously maintains weird, "floating" 2 lane routes all over the place while the respective counties are out maintaining 6 lane roads. What I mean by floating routes are small pieces in the middle of a route that are numbered while the ends aren't. My assumption is that in a lot of these instances, they are maintaining some other form of infrastructure in that area (such as bridges). Even still, many of them might as well be senators' driveways.

The trading mileage thing makes sense to me (evens out the maintainance load) although it is part of why weird routes get to hang around in obscure places.

[roadman65]

I would like to know why here in Florida FL 54 through Wesley Chapel, FL FDOT handed over the maintainence over to Pasco County between FL 56 and FL 581?  I know the FDOT got FL 581 that was originally CR 581 from FL 56 to its terminus at both CR and FL 54.  That is a swap, but it  makes no sense why they did it.

In NJ it makes sense why NJDOT and Ocean County swapped NJ 35 in Seaside Park and NJ 182 in Manahawkin.  NJ 182 became a secondary road when the NJ 72 Manahawkin Bypass was built and then extending the NJDOT maintainence to NJ 35's southern terminus at Island Beach State Park was a good thing for continuity purposes.  Plus, NJDOT was allowing Ocena County anyway to call their section NJ 35, even though signs at the NJ 35 & NJ 37 interchange showed NJ 35 only going north.

It would have made more sense to sign FL 54 concurrent with I-75 as many other DOTs would do that and leave CR 581 as is and maybe let Pasco maintain FL 54 between I-75 and FL 56.  FL 56 could begin from I-75 to go east to wherever it eventually ends.

[Alps]

I would like to know why here in Florida FL 54 through Wesley Chapel, FL FDOT handed over the maintainence over to Pasco County between FL 56 and FL 581?  I know the FDOT got FL 581 that was originally CR 581 from FL 56 to its terminus at both CR and FL 54.  That is a swap, but it  makes no sense why they did it.

In NJ it makes sense why NJDOT and Ocean County swapped NJ 35 in Seaside Park and NJ 182 in Manahawkin.  NJ 182 became a secondary road when the NJ 72 Manahawkin Bypass was built and then extending the NJDOT maintainence to NJ 35's southern terminus at Island Beach State Park was a good thing for continuity purposes.  Plus, NJDOT was allowing Ocena County anyway to call their section NJ 35, even though signs at the NJ 35 & NJ 37 interchange showed NJ 35 only going north.

Makes one wonder why NJDOT hasn't swapped other old alignments and mini-routes like 13, 59, 64, etc.

[florida]

I would like to know why here in Florida FL 54 through Wesley Chapel, FL FDOT handed over the maintainence over to Pasco County between FL 56 and FL 581?  I know the FDOT got FL 581 that was originally CR 581 from FL 56 to its terminus at both CR and FL 54.  That is a swap, but it  makes no sense why they did it.

In NJ it makes sense why NJDOT and Ocean County swapped NJ 35 in Seaside Park and NJ 182 in Manahawkin.  NJ 182 became a secondary road when the NJ 72 Manahawkin Bypass was built and then extending the NJDOT maintainence to NJ 35's southern terminus at Island Beach State Park was a good thing for continuity purposes.  Plus, NJDOT was allowing Ocena County anyway to call their section NJ 35, even though signs at the NJ 35 & NJ 37 interchange showed NJ 35 only going north.

It would have made more sense to sign FL 54 concurrent with I-75 as many other DOTs would do that and leave CR 581 as is and maybe let Pasco maintain FL 54 between I-75 and FL 56.  FL 56 could begin from I-75 to go east to wherever it eventually ends.

Completely my opinion. They may have wanted a more direct route to the west. CR 54 has that pesky curve immediately to the west of I-75. (The original routing of FL 54 was convoluted and has gone through many changes to streamline efficiency.) To tie in traffic for evacuations and just general traffic would be troublesome with Pesky Curve when you could just keep heading east on FL 56 to I-75, making the faster connection. Plus, with the completion of FL 56 to US 301, it will be more of a "bypass" for traffic heading to I-75/beaches than two-lane, congested FL 54.