There is a lot of opportunity for younger umpires who want to get serious about it.
In our association, there are lots of guys like me who started umpiring when our kids stopped playing high school ball. Someone in reasonably good physical condition who starts umpiring at 50 can become a pretty good high school and advanced travel umpire, but by the time we get enough varsity games under our belts to think about college, we're already older than the age at which most college umpires step away from umpiring. Also, people my age often have family and career responsibilities that don't permit us to pay the dues (work any game, any time, anywhere) the college umpires have invariably paid.
So our association is glad to take in people like me, but everyone acknowledges that we'll reach our ceilings pretty quick.
Because our association has contracts from 13U all the way up to D1, they are always looking for umpires who are young enough to become long-term college umpires and committed enough to take the training (they offer scholarships to the advanced training camps) and work enough games.
Those high school kids making $30 to work Little League games could be working high level games for money that is worth their attention by their mid-twenties if they stick with it and start climbing the ladder early.