Not if my team does everything in its power to lose the game.
* I am not obligated to protect the overextending midlaner.
* I am not obligated to make up for the fact that you outpicked yourself in champ select.
* I am not obligated to make up for the fact that you have 30CS at 10 minutes.
* I am not obligated to make up for you picking Yi jungle cuz your friends at school told you hes op, with zero games played as Yi (or jungler for that matter).
* I am not obligated to protect your turret if you decide that making a kumbaya-session in mid for 5 minutes is a great idea
* I don't have to make up for the fact that you play with a 500ms ping
* i don't have to make up for the fact that you were AFK for the first 3 minutes because your pizza got delivered
I don't have to play better than my teammates. I am not a pro-player, nor do I make money by streaming. My happiness and lifes integrity does not depend on winning games.
So if you make it needlessly hard for me to carry, chances are, I will rather have less stress and a loss, than suffer through a 45 minute game, which carries a high chance of being lost anyway due to the 3/15/9 guy still not figuring out that going 1v4 is a bad idea, even though he already died 15 times that way.
That doesn't mean that I advocate trolling, or throwing games on purpose, no. But I do take the liberty of not playing above the norm in such a situation.