Insurance coverage is not important in crypto currency. It just add to the expenses to the investors, further, how could a insurance company pays crypto holders in something happen in the exchange? We are decentralized and we move in our own risk.
I won't be needing to pay extra money for insurance since I didn't leave my coins on trading sites so it doesn't worry me.
However, I got what OP pointed out since centralized trading sites are subject to hacking so regardless in amount of trader's coins it will be covered by the insurance company but I guess it isn't easy as what it seems.