1. Because people don't know about it.I would be very careful and go forward with due diligence. If something sounds too good to be true, it usually is. If it was that easy and lucrative, wouldn’t everyone be doing it?
2. Most people are lazy and expect something for nothing. This is work. . . can you make money at it, absolutely. The more time you put in the more results you see.
Just because you don't know or do something doesn't make it wrong or a scam. Take the time and educate yourself.