Possibly one more hack will surely make them go low, but in the present scenario they have come up with their own reserve to keep the users without getting affected of loss. This could've never been possible with other leading exchanges. Anymore they'll make further developments to keep the security systems more effective with advanced security tools.
Seems they have understood that if they get hacked again they will lose many users so they must be focusing on security.
Binance is holding too many coins from people that do not want to download and sync blockchains for every coin they have. That is the biggest reason people target exchanges.
Ye, it's a big mistake. But Binance is full of such traders that don't want to hold in the cold storage because it's impossible. I'm afraid MtGox recurrence only. Holdings 'as is' not bad. But with too much pseudo traders it can become dangerous