Many dissatisfied reviews are based on the lack of attention and the guilt of the people themselves, only possible risks that are beyond our control, are often underestimated, for example, unsafe or fraudulent actions of the exchanges.
Perhaps you`re right. But to assess these risks is difficult, as is rarely the case. With some people never. Among the frivolous majority there are, but there are also cautious people.
If hacker hack ecxhanges traders can do nothing with it. There is 2factor verification but it does not help if exchange will be hacked.