Most hobbies are infantile. Dancing, swimming, bowling (grown up marbles), boats, train sets, football, bashing a drum, motorbikes... all things you’ll find five year olds are into. Most of us don’t change that much, getting fat n old doesn’t preclude them from enjoying the things they do. An imaginary list of approved activities once you hit a certain age or weight is sadly restrictive. I just see it as someone indulging in whatever turns them on even if it appears a bit silly to me.
I can’t argue the reality gap is often pretty comedic and the tantrums that can go with them are very funny.