If Dads aren't coaching many of these teams there is no one to do it. Can someone explain why it's wrong to coach your own kid. I have no problem putting my kid on the bench when he's not cutting it. I know that's not the norm, but there are a lot of fathers out there that coach for the right reasons. And often times the coaches kid(s) are some of the better players on the team, that's a fact.
It's also a fact that sometimes they aren't.
You answered your own question - it's not the norm. And when something is so badly skewed for the wrong reasons, people will object.