Exchanges are meant for trading only, if you are going to use them for staking then you are in risk of losing funds.
Youre wrong at this point, theres a lot of exhange that give you bonuses or rewards for staking specific coins at their platform. And if staking at exchanges means a risk of losing funds, then theres also risk for trading there. Risk can be found if theres a risky situation made by the exchange. Ex : Th exchange has bad issues regarding trust. Theres few of them, but issue stays issue. But regarding funds, issue needs to be taken seriously.
Even exchange with good reputation can happen so we might have chance of losing all our funds.If you want those bonus you can keep the tokens on exchange but its not safe to store that is my point.