Although growing fast, they're still a relatively small company, and having 24/7/52 fraud screening people on staff is more than they've chosen to offer.
Paypal is obviously different. Paypal has been known to freeze accounts much quicker than CCs, to the chagrin of some of their customers.
They are very practical, and use "what works."
It's not clear how you're losing business because of not opening a new account.
They do have automatic fraudinator, with human intelligence added in selected (proprietary) conditions.
There are occasional complaints like yours here, so to some extent your reaction is normal and reasonable.