Honestly, I think a lot of it is just the friction of payment interfaces, endless redirects, anticipation of bugs in those fragile workflows...
There's a lot of things I won't pay $4.99 for because I'm too lazy to tap through five screens and try to remember my CVV. If I could just press one button and the five bucks get charged and that's the end of it, the instant gratification would be hard to resist.
I don't think that Paypal (which can do that) helps that much. It really is a mental hurdle. I understand it. It's: "Maybe I can just google around a bit and solve my problem." It doesn't matter that they can't. It's the fact that they think they might be able to that interrupts the purchase.
As a 2016 MBP owner, I find myself making a lot more impulse purchases on websites that support Apple Pay simply because all I know that all I need to do is put my finger on the Touch ID sensor.
There's a lot of things I won't pay $4.99 for because I'm too lazy to tap through five screens and try to remember my CVV. If I could just press one button and the five bucks get charged and that's the end of it, the instant gratification would be hard to resist.