As everyday hustle and bustle of life slows down as we get older.... or at least for me it did, then there is more time for activities we used to do all the time as kids. So yes there are a lot of us older types actively cycling.
Possibly a lot of us that are ADD (ADHD) love the adrenalin rush of speed and endurance part of it. I know I do. For others, maybe it's a good social crowd to identify with.