The reason I think this is because it's not safe going door to door. I also think that people get annoyed by kids knocking at the door asking if you can buy their product. I think companies should try thinking of other ways to raise money instead of going door to door. There are the obvious dangers of selling to strangers, of course. But there are other problems people should be thinking about as well.
Kids get the idea that only adults can make real money.
This leaves them open for all sorts of fraud and harm. I guarantee you, it's millions. Even if schools and parents make extra effort to keep their kids safe while selling, that still doesn't address the problem that the kids aren't paid a percentage per item sold for the work that they do. Let kids learn about volunteerism in a wholesome environment. Standing behind the cake sale table is a different world.