Online card games ask if you’re sure want to resign when you close the game.
Do people, in real life, say “resign” when they decide to stop playing? I say “quit”, and so do the others I’ve played with. It is true that I rarely play card games, so using “resign” may be more common than I think. It might also depend upon the kind of card game. For instance I never play bridge.
This is really important, ya know. 
Peace,
mangeorge
Nobody likes a quitter.
I say “concede”. But I picked that up from playing Magic, where it’s a common term.
The online version of Magic uses “concede” as well.
Actually, neither do I. I much prefer resigners.
Even if you’re winning?
The time honored tradition of my He-Man-Woman-Haters camping/wargaming group is a mock formal exaggerated “Ah surrender, Sur” with a slight bow. Then we consume various intoxicants and shuffle for the next game.
The problem with resigning is that the next thing you know, you get knockout gas piped through the door and you wake up in some Welsh village where you have to play cards with actual people.
I think there’s a plausible reason for an online site using that term - most of the time, “quit” is simply used to end a program. Some quits might even save state, as it were, when you open them later. They need to make it clear that if you leave the game, you are losing it. Asking “Do you wish to quit?” might be unclear on that point.
Meh, signing once should be enough.
I’m resigned to the inevitable truth that there are going to be posts like this one.
Even if you’re winning, and for any reason except in return for a consideration from your opponent.
You might have to leave to catch the last bus, for example.
Ah, the infamous Peppercorn MTG card.