Some of them are just scammers but not all of them, a lot of them keep to their promises. The rest are just there for the purpose of making money and when the money is no longer coming as they expected they will start to dump the project and taking away with them the money that belongs to their investors. Thats why you should study an ICO very well, its not just all about whitepaper.
Because of the lack of regulation in the cryptocurrency market, fraudsters can commit fraud through simple structured projects and are not responsible for it. This is really bad.
I dont really know that for sure, but I do know that even if there is regulation some of these scammers will still make their way through to the community to scam people. You cant stop it, the best you can do is to avoid them. I remember reading an article on Cointelegraph.com on July 2018 which says that according to a new study 70% of the ICOs conducted in 2017 were scam. And around October of 2018 another statistics claimed that 99% of ICOs are going to fail. So the best you can do is to avoid them.