There are a number of routes where 'negative cant deficiency' would greatly help timings. That was a basic premise of the British APT, and the pendulum trains that followed it. Atlanta-Chattanooga-Nashville is a place where tilt would almost be necessary even at 79mph track speed.
The 'catch' is how you implement tilt on double-level sleepers, or conventional 'legacy' equipment (I believe the PRIIA spec cars were designed to accommodate tilt, but I don't remember the degree). Clearance to possibly-wobbling stack equipment on the adjacent track is a consideration here.
Remember that unless the tilt system translates the carbody sideways as well as tilts it, the actual geometry between wheel and rail is less favorable for stability, not more: the effect of tilt then being solely on passenger perception or comfort.
Another 'catch' is that many of the lines that would benefit from tilt are also occupied by heavy freight, which would have to be delayed or rerouted to allow even the 60mph speed mentioned. It might not be 'worth' the capital and maintenance expense to implement full tilt if you have to operate 'one-speed,' at PSR-optimal speed to boot, for too much of the trip...
