Starting to write late in Life.

My Son, my oldest, will start college this week at Washington State University, and my daughter will be starting the 9th grade next month. These two events have me thinking I am old and getting older. I have also realized that most writers started their careers at a much earlier age. Think about some of the big names, I mean I do not have to list them here we all know them. These people, these, authors, these writers normally start writing in their 20's (some in their teens), at most in their 30's. I know there are exceptions to this but we can all agree their are not too many widely successful that started in their 40's. (I know you can point some out, but I already said there are exceptions.)
I questioned this an wondered why? Ability? No, their are older people (more than you can imagine) who write way better than younger people. Yes, they may not write books, poetry, or other such works, but they do write in their jobs: reports, evaluations, and various communiques. They take pride and write some of the best flowing prose you can imagine. (You should have seen some of my evals in the Navy).
Is it imagination? I know people say that older people are not as imaginative as younger people. Not true, it is not because we lose our imagination, it is because we have to face reality to make a living and use are imaginations less. (We use our imaginations to take mental breaks during the day, but we call it daydreaming) I know my imagination is still as good as it was when I was a kid. (Except I don't draw spaceships anymore)
I guess why most of us realize that, well, it is hard to make a living writing and this concern can trump the dream. Yes you can work and write. but at what cost? time with family, relaxation time, or other?
I wish I could get a huge book deal and live off my writing. (Might, most likely, never happen). The thing is I write because I love it and I can exercise my imagination and feel young. I want people to read my works. I want a fan base. I want to have at least one person say "I like it, I love it."