I think it's definitely dependant on your site's demographic and whether or not you sell internationally as well as how the icons might fit into your overall design (if you're trying to do something different or modern). That said, I think the other comments here are correct in that it helps legitimize a site as well as give some international users an idea of what cards are accepted. Side note: I made some credit card icons in sketch a while back. Here ya go: https://dribbble.com/shots/2415614-Credit-Card-Icons-Sketch-File
I think it's definitely dependant on your site's demographic and whether or not you sell internationally as well as how the icons might fit into your overall design (if you're trying to do something different or modern). That said, I think the other comments here are correct in that it helps legitimize a site as well as give some international users an idea of what cards are accepted. Side note: I made some credit card icons in sketch a while back. Here ya go: https://dribbble.com/shots/2415614-Credit-Card-Icons-Sketch-File