Paypal was already a mature product back then. Literally every major bank already offered custom-branded payment pages and an API to process credit card payments. Why would you bother to build Chargify to offer custom-branded payment pages and an API to process credit card payments?

Well, because Chargify is miles better than Paypal and banks. Maybe that guy next to me has a face-tweet-o-base idea that's miles better, too.