[hakfoo]

From my perspective, PayPal was always distracted by what it wanted to sell to consumers, which impacted what it offered to retailers.

All most merchants wanted was "let me accept credit cards with quick and easy setup, even if it's expensive." (Hence the success of Square, Stripe, etc.). All they needed to do was to offer a few APIs that acted like every other credit card gateway, and they'd be fine.

But instead, they went whole hog on telling consumers "you never need to give the retailer a card number." Now, I'm skeptical this was ever a huge selling point, but it means that any API they can ever offer will always be a nonstandard mess to work with because it means you're going to have to bounce users off your site to finish checkout.