I would like to open a civil, logical discussion on this saying. I'm curious about a few aspects about it. First of all if you say it, do you legitimately feel that one gameplay mode excuses behaviors or even means you should put less effort into the game? Why do you feel that way? Can you explain it?
I was thinking also about a time I visited Italy and I was pretty put off specifically at one thing: line ups. Did you know that it is culturally accepted in Italy to just butt ahead in line ups? You have to extend your elbows out and jostle your way, "fight" for your space to get to whatever you are waiting for. (I'm Canadian but I've also lived in the US, and I can say that the moment someone ever tried to butt ahead in any lineup that person would absolutely had a talking to by several people.)
It dawned in me that this behavior started somewhere and enough people just accepted it for it to become a cultural norm. Not enough people spoke up about it.
It seems that some etiquette in ARAM is similar now. We are meant to just stuff off your 1 min afk at the start of the game(even though, arguably that 1st min can actually set the tone for the entire game), or that you behave like a "ping general" pinging players trollingly all game, or that you deliberately take health for just you even at 100% life with 3 team mates at 40% life, or just not even put out 50% effort in the game, or if you link players gear or skills (even if that player is doing statistically the best of all 10 players) that's acceptable, or the miriad of other player behaviors. All actions justified or sluffed off as "LOL it's just ARAM!"
I would love to see some insight into this justification.