Simple, They just want to get an easy way of earning money. Cheating and stealing are part of our human nature. We do have a devil inside of us and we are fond of taking advantage to those people who we know are vulnerable. Scamming has been around in any type of industry, and we can't contaminate those people as they can easily jump from industry to another. Some people tend to scam due to influence of other people, urgency and etc.
Exactly, they scam because of money. Maybe because they need it for something or they are just doing it to sustain their needs and wants. Everyone has its own reason why do one thing. For those who scam it was easy for them to make money by doing that thing. So they grab every opportunity that they see and not thinking of others feeling. They are just always thinking of theirselves.