I sell a software production online. The purchase page has a simple credit card payment form, and off the side is a small "PayPal" button an an alternative payment method.

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.