The excepted lifecycle of an armored vehicle is decades of crew training followed by years of low intensity combat. This historical intensity was so low, that casualty rate is lower than dangerous civilian jobs and health and safety concerns make a meaningful difference.
The united states, being a nuclear power surrounded by oceans, will not be fighting a war in defense or national survival with these vehicles. This is doubly so for vehicles developed to be lighter weight and thus air transportable.
In those expeditionary, optional conflicts, the question isn't about making sacrifices for a greater cause, it is about getting results while making no sacrifices.
In higher intensity conflict, something like MPF is marginal to begin with when stuff like nuclear strategy, air superiority, sea control, long range precision fires and such start to weight in. It is not like a slight improvement in MPF performance in any factor would change much here. I mean, T-90 or T-55, they are all steel box that go boom when on the other side of PGMs or mines.