On another tack, with advanced age and experience comes (ideally at least) respect and recognition.

An older individual knows things that the 'youngsters' do not. They might be sought out for advice. They might have a group of up-and-comers trying to impress the sage, and so are ready to do their bidding physically.

An older person might have a high status in their community or profession. This then reduces the amount of physical effort they need to expend, as their roles become more academic/teaching, rather than the grunt work.