I understand your points and get that it's frustrating if your goal is all about winning. Track and Field is kind of a different animal in that kids can win even if their team doesn't win. Also, when kids transfer, doesn't it open up opportunities for kids that might not have had a chance to play?
Forcing kids to sit out is a tricky thing since they have a very limited window to play as it is. College is a bit easier for that with redshirt years that high school doesn't have. I just don't have a problem with kids transferring to a place where they feel they can succeed for whatever reason be it for sports, academics, social, etc.
If schools have a problem with kids transferring out routinely, I'm guessing there are other problems than just the kids/parents. Maybe the schools need to do a better job recruiting their own kids.