It's true that 'not your key, not your coin', and that there are several wallets and services available to cover yourself.
There may be a point at which any cryptocurrency (whether Bitcoin or another) is held on exchanges/wallets run by small/new companies.
The small players have limited resources. How do they ensure they are sufficiently protected? Why don't there be hacks every other day?
No exchange is safe, the scammers are getting better even if they have tight security there's always a possibility of getting hacked, you should never make exchange wallets as your storage, only put coins that you will trade and only trade on Big and reliable exchange so even if there is an incident of hacking, the exchange will cover all their trader's coin's and even if they guaranty your coins is safe, still don't go for their service you should be the one responsible for your coins.
No exchange is safe but there is lesser risky among them so we should stay on that one but even though they are top still we shouldn't put any huge amount which can hurt us badly when things comes in bad position, we should always think about withdraw the profit always we take on the exchange and store it on hardware wallets since putting it there will really give us huge risk on what you said hacking or maybe an inside job incidents.