I suspect that many of the players are teenagers and this can be a reason so many characters are teenagers too.
When it comes to making an elderly characterI don't think it would be so difficult.
I can see how you are thinking, because I have asked myself those questions too. This char isn't old exactly, she's 33. But the questions about skill level and flashbacks applied when I made her. For a while it felt very weird and unrealistic that she wouldn't get more skillpoints than people she is twice the age of.
But this is how I have settled for thinking.
It's not necessary to write flashbacks - I can write flashbacks if I like, but nothing and no one forces me to do that - I don't even need to write lots of character history in the character sheet - and if I'd like to tell lots about the characters past it could as well be done by storytelling in the present - could make for an old person that has lots of stories to tell - which would be quite realistic.
Also, It's not like all old people need to have sorts of advanced skills. An old person can for instance be competent in something - lot's of older people are competent, but not experts. And people have quite often not had time to learn lots of skills if they worked and had a family and so on - instead it can that they have more time to learn new things when they are old, they can be interested in new things that they weren't interested in when they were younger, and they can also have lost some skills that they had when they were younger - a person can have been a quick runner and good fighter when he/she was young but when he/she is old that skill is gone - then again he/she can have started to take a newborn interest in a craft, or in philosophy or other things that doesn't require physical fitness.
Thinking the way I described above I could easily make a person of age 70+ and have no problems with it. Perhaps the problem would instead be to find people to roleplay with if the char isn't "young and VERY beautiful" ?