The issue is, that even though most people assume they are aware of the risks, they too often assume they are the ones being able to recognize all the dangers.
"I'm not in danger, I'm using only this one service which I used for four months already and had zero issues, so I'm sure it is perfectly safe..."
Some then assume they are so poor crypto-wise they do not need to worry yet, but I could imagine a scenario in which a currency suddenly increases in price, going to the moon.. and then a random trading site goes rogue and steals everything from accounts of the users.
It's always too late to react when the worst has happened.