Yeah they are new paypal 1% of all transactions. They couldn't afford any shady exposure. If they made an exchange it would be conflict of interest.
But what pisses me off is why the hell do these companies get investors when they don't need it? They dilute their own interest. They don't need capital at all.
Connections can mean a lot more than capital. Raising money from Peter Thiel in the payment processing space carries a certain cache with it. Also as Tony Gallippi pointed out they hadn't yet run through their last round of funding, but they were going to have to raise some more along the way to being able to bootstrap the rest of their growth.