I think 'being a good sport' includes letting the opponent have the win, giving them points towards the VS ladder and by extension allowing them (and yourself) to carry on with the day and to the next match.
If you truly cannot win, you aren't "giving them points"; you earn those points by defeating your opponent so
if you can't win your opponent has already earned them. You
can save both players some time if both players are
only grinding the Ladder Rewards. Even as a player who is often vocal in my criticisms of the game, I still can enjoy
actually playing. Indeed, my biggest criticism with gameplay is that we too often have a format where gameplay becomes one-sided so that one player either can do nothing, or do nothing that will ultimately make a difference as to the game's outcome.
Do as you see fit, Perfect_Shot. I'm not telling you how you have to play, and I strongly suspect the majority opinion agrees with you.
I just want to explain one of the other views. To me, agreeing to a game is agreeing to see it through until the end, because there is
always satisifaction in finishing the process. I use "satisfaction" because I mean that it is irrating and unpleasant to
not finish the game.
All of this is before we consider things like someone trying to finish up a Daily Challenge (especially KO challenges), testing a deck, etc. The
compromise I suggest is considering how much time is really being "saved" for both players. If I
truly am in a place where I can't win, or learn anything, or still work on a Daily, I'm not conceding unless I'm
sure it is a serious time savings. After all, I might be costing my opponent more time because they
were practicing or working on a daily. If I lose in two turns, odds are "Draw, Pass" finishes the game in less than two minutes.