Not everything that's bad. A sucky API and UI isn't because of regulations.
If you want paypal, why not use PayPal?! You think Stripe could turn into an multinational bank/processor/transmitter/card network/tokenizer/anti-money laundering quasi governmental entity plus whatever the hell else PayPal is without having the same problems PayPal does?
I've read of stories of people getting burnt by getting significant amounts of money frozen that they had left in their merchant PayPal accounts (without transferring it to a bank) for inane reasons. Not holding on to the money eliminates that worry and builds trust, doesn't it?
* allow true multicurrency operation - a Stripe client in any country should be able to accept funds in any currency Stripe supports.
Case in point, as a Canadian, I can accept only USD or CAD. But I have clients in the UK, and am stuck using Paypal to accept GBP directly.
* let people hold money into their Stripe account instead of transferring to a bank immediately
* let people transfer money from their Stripe balance to any other account's Stripe balance for free (PayPal charges a fee for "cross-border" transactions)
* make it possible for marketplaces to pay their workers through Stripe (PayPal and sometimes Payoneer are the only choices now). Workers can then withdraw to their bank accounts from Stripe balance, or use it to pay directly for other stuff on the web
* have a low commission for merchants, if not free, for payments of goods using Stripe balance