Well good idea too to make a deversification of your asset in multiple exchange because if one freeze or even get compromized still you have into other exchange, well seems its sometimes getting lazy to transfer back and fort your asset into your wallet to exchange so sometimes we let it there in the exchange itself. but still this is aint our money its their money once its on their exchange.
Many people dont want to have the headache of creating a software wallet. I dont think its a headache, rather a bigger headache is going to happen when the exchange goes down with a huge amount of funds still intact there.
Because no one can predict when a hack or a government seizure of a website is going to happen and nobody is ever going to know how long the process after that is, its better to avoid it from happening.
Now it will become different story only if you will store your funds for a long term in an exchange with a longer position id recommend into using your wallet now than the exchange as your wallet.
I think users on this forum know this but a large chunk of regular users are not on this forum but away and only use the exchange and dont read stuff getting posted here.
Hence victims will always happen in such hacks, but at least the users of this forum should be safe.