I don't think they ever think about life past 100k miles, which is right around the point you should change the transmission fluid. When I was shopping for cheap early 2000's cars last year it was really common for otherwise reliable cars to have automatic transmission issues. Honda, Mazda, didn't matter. I wonder if it's because the transmissions themselves are bad it if nobody bothered to service them since it's not supposed to need service "for life."
ALL ATXes are intentionally designed in a fashion that encourages and eventually will lead to failures.
Specifically the wetted area of the transmission contains friction materials (in the clutches) that inherently shed into the fluid. This is like putting brake dust in your motor oil and over time has the same sort of result.
In addition the filter is a joke compared with even full-flow (say much less bypass design) motor oil filters and is intentionally inside the case, making easy changes impossible. Would you tolerate having to drop the oil pan to change the engine oil filter? Well?
Third, they're designed (on purpose) so that draining (and thus changing) the entire
fluid load is nearly impossible. Specifically, the torque converter is designed in such a fashion that it cannot be drained nor does it drain back automatically when the car is shut down and it holds a LOT of fluid. Would you tolerate an engine design that only allowed you to change 1/2 or so of the engine oil, forcing you to leave the other half of the dirty oil in the engine?
And you wonder why they fail? They're designed to fail
once you get into the six-digit mileage category, and avoiding those failures is difficult at best.
It's much like passenger diesel DPFs which are (1) non-separable from the cat so you can't remove and clean them -- heavy truck units, on the other hand, are SEPARATE (for this exactly reason) and (2) three to five times as expensive as they should be due to integration with the cat, which does NOT typically wear out yet MUST be replaced when the DPF wears out. That too is an intentional design decision which is why I will never own a modern-emissions diesel passenger vehicle.