Do they? I'm sure there are some, but there's plenty of examples of that not being the case.
Looking at other United stars, Beckham, Butt, Giggs, and Gary Neville all made their debut aged 17. None of them were going off the boil in their late 20s and none had declined anything like Rooney has. Giggs was playing to an incredible standard into his late 30s.
Some pretty massive revisionism going on here to pretend that Rooney couldn't have taken better care of himself or that's had nothing to do with his decline.
Nicky butt? Don't even know what he was doing in his 30s
Beckham was in America
Neville massively declined and admits he should've retired sooner.
Majority of players out there decline when they hit their 30s, especially players who have been playing at the highest level for as long as Rooney has.
I personally find it a bit mad how anyone can question his dedication to the game considering all he has achieved.
Even now, at 32 he's probably the best player for one of the biggest clubs in the country.