The USCF caters to the kids because they constitute the bulk of their membership.
As a youth chess coach, I find it extremely difficult to think of a single tangible action that the USCF has taken that benefits youth players. On the other hand, the income generated from their membership fees keeps the organization afloat.
If the USCF were successful in promoting youth chess, we would not see the largest numbers of young players in states where scholastic tournaments are not USCF rated. Most years, the Washington State Elementary Chess Championship dwarfs all other youth events except nationals. A small percentage of these students are USCF members.
By "professionally," I mean well enough to earn a living playing chess. That really means GM level. Indeed, many GMs can barely make a living solely from chess. I think that most (but not all) reasonably intelligent people can, with sufficient effort and study, get to about 2000, but it's very difficult to advance beyond that unless one is very talented and also extremely diligent (and has access to the right teachers/coaches).
Many kids plateau below 2000 because they lack the time, dedication or coaching resources to get higher. Moreover, many kids lose interest in chess either when progressing further becomes too much work or when they develop other interests that have greater priority than chess.
There is absolutely nothing wrong with that. Millions of kids learn music and how to play an instrument. Some quit when they get to junior high school, but some continue playing in their hgih school band or orchestra. A few even continue to play in college, but only a very small percentage end up as professional musicians. This does not mean that scholastic music programs are a failure or that we should stop teaching music to young children.