Interesting observation!

Guess many turn entrepreneurs themselves. I have seen some enterprising one's save/borrow and start their own small cafe's /restaurants /shops /taobao shops /trading cos etc either individually or in partnerships.

Don't they get "promoted" to bustboys/girls ? I think there is a larger amount of old people removing people leavings from tables at mediocre restaurants. 

I agree that most likely there are some of them that are unskilled, perhaps they come from a family that couldn't put them through school. But I am sure a lot of them are young brilliant people who through perfecting their exam cheating skills have a diploma from some uni, and they are just waiting to land a job.

A lot of them commute from their conveyor-belt job to their overpriced shared bedroom. They're too tired to hang out most of the time. They shower, then sleep, wake up smelling bad, go to work to smell worse, then go back home to shower. Yet their beds smell bad too. You'll see them at family engagements. Some hotels rent out space to these kinds of workers.
When too old to handle it, they retire to the countryside. All that economic growth has to be carried on somebody's back. Be glad you're not Chinese.

Childhood = Rote-learning time. No time to play

Young adulthood = The Meat Market. Don't sully those good looks with dirty hands.

Middle age = Work like a dog is what you are good for. For the family.

Old age = Live off your kids if possible. Ideally out of sight in a farm upstate. Hospital scam otherwise.

im just guessing, but it might well be that it's a more recent demographic trend. That starting 10 yrs ago young people from the countryside started showing up in cities to get service jobs that didn't exist before.

The older people either stayed behind or moved to the big cities to work construction or cleaning staff etc type of jobs instead of becoming waiters/service workers/retail clerks.

It might just be that those people haven't had enough time to get old yet. Or that restaurants deliberately only hire young people and then the older ones either have to go back home or get less visible low-end jobs.

This question is dumb on so many levels. First, you're Chinese you not used to seeing what you claim. Secondly, what you're saying doesn't apply in every situation. Example, if you take the fast train, you'll see younger pretty girls especially in first class. Normal trains you'll see the normal people working. Same with upscale shops/ hotels and low end. This is because China openly discriminates along all lines. Stewardesses are let go after they turn a certain age or gain a little weight from pregnancy. So where do you think they go? (dumb question) They get another job.