I don't know if this is your case, but usually it's because one ends up sitting a bit "sidesaddle". On my PA-28 this is definitively the case.In my case, the cushion ends up bottoming out in the inside rear edge corner, leaving an incredibly unpleasant hot spot against the seat bottom metal frame in the outer glute area of your hip. For me it has to do with being V-framed due to weight lifting, thus having the need to offset my butt seating away from the wall of the airplane in order to gain shoulder and arm clearance from the sidewall, where the seats in the PA28 were not offset from the sidewall at all. As a result, the cushion gets quickly worn out with the uneven seating pressure.
I probably need memory foam or some sort of upholstery that is more resilient to that kind of uneven seating pressure. In reality I just need an airplane with better seat offsets from the sidewall. I've only done long flight in Piper products, so I don't know if Cessnas are better on this regard. I believe Cherokee Six frames have the seat pan offset from the seat tracks in an S curve on the seat beams. I'm def looking at these non-performance metrics in more detail when it comes to my upgrade airplane.