Seems to me that NC and TX are the two states most serious about Interstate construction! Even if they're stuck with out-of-place routes that may never connect to their original counterparts in our lifetimes.
The reason for this in NC is two-fold: (1) High gas tax, which means more revenue, and (2) the "equity formula" that until a couple years ago directed much of that revenue towards rural freeway construction, to the detriment of urban areas.
Other stub interstates include I-26. The construction of I-26 over Sams Gap on the North Carolina side really is an engineering marvel: 60mph speed limit, very gradual curves, and SIX LANES through extremely mountainous territory. And 12 years after it opened, it carries something like 9000 cars per day. The Tennessee side was completed earlier but is much curvier, has a 55mph speed limit, and only four lanes wide with no room to widen in a median - and IMO is probably a more appropriate design given the amount of traffic it carries.
Interestingly, I-26 and I-74 both have Columbus, OH as a planned northern terminus, so if I-74 is built as planned, I-26 could connect into it maybe somewhere near Williamson, WV, and travelers could just take I-74 north to Columbus from there.