It's not zero risk; changing my card numbers after a compromise is an annoying process given the number of places I have to do it. Not having to provide that number to the random e-commerce site I'm trying to buy something unusual from is helpful, and reduces the risk of me having to spend an afternoon making sure I switched cable, internet, Github, Patreon, Heroku, kids' school lunches, music lessons, and fifty other recurring payments over to a new card number.

(I also get to skip entering card and billing details every time. Given the number of sites that see fit to use a special non-standard widget for the state field, that saves me time and annoyance on every transaction of this nature, too.)