The way they run it.
Here, at least, it's run like the Mafia. Everybody knows who is "in" and isn't. Constantly reminding us to contribute blah blah. Each branch is literally compared on how much is contributed, it's even tracked at the individual level. The idea of giving incentives to groups who "outperform" only means those that don't contribute are rejected by their peers. Luckily our whole branch agrees that we want nothing to do with it.
It would be fine if it were all anonymous, but it isn't.
They even have a giant "dollars contributed" sign at the front gate of the post.
I'd rather just hand my local Boy Scout troop $100, no need for the Feds or anybody else to be involved and know what I'm doing or act as a middle man.