Why the fuck would someone keep cash in a central repository if the whole purpose of bitcoin is to be de-centralized? It's like, hey, I have a car so I can get around town any time I want, so let me park it with a bunch of other cars in a dark open lot 2 miles from my house. Sure, I have to take a short bus ride to get to it, and it could be stolen or broken into at any time, but that's the price I pay for convenience, versus just keeping it in my garage where it's much more inconvenient for anyone to steal or damage it. (?????)
A website is not a bank. There are no armed guards or vaults and there is no federal insurance for your bitcoin. You're basically all handing your money to some guy who keeps all the coin on the second floor of a corporate office with a single old dude standing guard at the elevator. It's totes hard to get past that guy, because like, he has a badge and a hat and everything.