all they care about is making you buy more and problems start when you decide to withdraw.
A common problem. Open an account - no problem. Link a payment method - no problem. Deposit some fiat - no problem. Buy some bitcoin - no problem. Withdraw that bitcoin - hold on a second! We need selfies and documentation of all your income for the last 3 years!
I also see reports that people have problem withdrawing other coins and not just cash, so it could be a much bigger problem with Coinbase exchange.
It wouldn't surprise me in the least if most big exchanges, not just Coinbase, are fractional reserve at this point. Huobi (the second largest exchange in volume) have been caught using users' deposits for investments, loans, and other purposes, without their knowledge and consent. If you are sitting on a million bitcoin as Coinbase claim they are, then it's just good business sense to use that to make more money. Not so good for you customers, though. Also easily done when your cold storage is deliberately structured so it is impossible for any outside entity to identify how many coins you are holding.