I just looked at Interstate 90 along this segment on Street View. The pavement looks ghastly. Also, what segment of Interstate 55 are you refering to when you say "everyone's favorite I-55 section"?
Between I-80 and Weber Road.
https://www.google.com/maps/@41.5547791,-88.1806159,3a,75y,186.24h,84.98t/data=!3m6!1e1!3m4!1sYnbHgkIXZ-u8Fw2KoxdU9A!2e0!7i16384!8i8192
https://www.google.com/maps/@41.6238457,-88.1636653,3a,75y,181.59h,70.3t/data=!3m6!1e1!3m4!1sOk0oF02riICmpHh7ocajtQ!2e0!7i16384!8i8192
I swear, the pavement on 55 is a shade of orangish-red from STL to Springfield. Parts are bumpy as all hell. That reddish pavement is common in Mississippi and TN and such (due to iron) but not in the midwest.
I've noticed this too. They ought to six lane 55 from 270/70 to Springfield. Lots of trucks use 55.
I live in the area and used to drive that stretch (I-55 from I-270 to Spfld) a couple times a week. It had terrible traffic from I-270 to at least Livingston, IL (exit #37, I think) and justification could be made for widening to 3 lanes without even considering future growth.
It's been a while, but I remember I-55 only being six lanes from Lincoln to the south end of Sangamon County. Except, of course, where you need it as you go around Springfield on the I-55/72 concurrency!!! The whole of I-55 in Illinois should be six lanes considering the traffic. I was so grateful when they widened it around Bloomington/ Normal, which is where I normally exited to head up I-39 to Wisconsin.
It's still that way. I guess the latest 5 year plan has rebuilding of the Southern I-55/I-72 Interchange in Springfield programmed (it's the Northern one that needs it much more urgently). Also, I think they also added an extension of the 3 lane section to past the Sangamon River now, but of course, this still leaves the section actually within Springfield still in need of a major widening/upgrade.
They do need to widen the entire thing to six lanes, but other than Springfield, the next sections that need to be the top priority are South of I-80 to at least Braidwood, and probably even Dwight. Then the section in the Metro East North of I-255 to at least I-270 and probably through the whole of Madison County. Those also would be the most challenging sections with lesser ROW. Once you get out of those sections, the rest would be relatively easy and just require slapping an extra lane inside (and of course rebuilding any overpasses to accommodate where needed). Don't hold your breath, though. Illinois, on the I-80 rebuild plans through Joliet seems like they might not even have six through lanes on the entire thing, although I am hoping that common sense will prevail before they start building that.