Some of us have learned these things to experience. We could easily stay away from scammers if we don't trust people easily. Also, we must be keen and observant about people's intention around us. We should do some research before doing a certain step like choosing an exchange or a trading site. Being scammed is frustrating so we should protect our earnings.
True ,some of us have learnt the lessons but still there are people who are being scammed ,so spreading a small word could save somebody's hard earned money !