I think Paypal has very strong brand recognition with the average consumer for such an esoteric product (online payment processor as opposed to say candy bar). Anecdotally many people enjoy how easy it is to pay with Paypal and that they have a perceived extra layer of protection. This is doubly true for this case since credit cards are historically not as wide spread in Germany as elsewhere (and thus Paypal linked to your bank account becomes a pretty attractive option). Most "Paypal is bad" stories I'm reading are at the expense of merchants not buyers. As long as they control buyer mindshare it's hard for merchants to opt out imo.

I wonder if there's studies or analysis on this (expected revenue loss with no Paypal option). Were I to start an online shop I'd prefer something like Stripe but would be pretty worried about missing out on a lot of revenue.