Despite the fact that the PayPal button is tiny compared to the credit card form, a full 2/3 of customers use PayPal to complete the purchase.
That's why people use PayPal, because a large percentage of customers prefer it over credit card payments.
Also, I prefer PayPal disputes because they don't charge a chargeback fee like credit cards.
And the fewer places I have my card the better. You might get the same results with Amazon Payments, unless you have an international audience.
This is exactly why I use PayPal. I would far rather use a more reputable interface system, but I am NOT keen on handing my CC info out to every shop online.
First you have to figure out how to use the webpage / app to get the virtual credit card number. Once you know, you still have to log into a separate service and click a few buttons. With PayPal or Amazon Payments you just click your password manager's button to log you in right in the checkout process on the same webpage.
Credit cards have become more common here recently but for a long time it was either Paypal connected to the customers bank account or plain old bank wire transfer. Sure, there are some niche services like Sofortüberweisung, but they never gained the status of Paypal.