because they think they are being perceived as "unsportsmanlike," which again, many have said isn't the case.
It is the case though. I went through the first 3 or 4 pages and here's a series of quotes that quite clearly are saying that people who don't point out a mistake or missed opportunity are being unsportsmanlike.
Winning because someone is forgetful is no different than winning because they are an idiot, which is a terribly hallow achievement.
I would always remind a player if he forgot something and I noticed whatever the game. Its called sportsmanship.
I think intentionally trying to win on a mistake makes you a bit of a dork.
You are by no means obligated to remind your opponent not to forget about an ability or an action but at least be honest here: you don't want to play X-Wing at that point. You just want a check mark in the 'W' column.
It is binary, in my opinion. If you're not being a good sport, you're necessarily being a bad sport.
So clearly there are a number of people posting in this thread who are explicitly calling anyone who doesn't play by how they define the "spirit of the game" to be poor sports. If I wanted to I could go back through the last 10 or so threads on this topic and find another 15-20 cases where people who don't forgive mistakes or point out missed opportunities are called bad sports.