I was always under the impression that sites like this didn't even store user funds.
Don't know why but, I was thinking they were just using the APIs of other exchanges to make the trades and skimming a small % off the top to make their profit.

There were a few of them in the past that operated that way. Put together a pretty interface, no real KYC, and just take a small cut.

Saw this when I went to do a small swap of some alts I found a paper wallet for when cleaning up and didn't want to be bothered finding an exchange that actually traded them and setting up an account and so on....

-Dave