I see people in competitive telling me to give them the 2nd half and now I've seen it in pro play. Why do people fill it to half and then let a team mate defuse the 2nd half?

So yesterday I was playing my second ranked game to get a rank, at the time I was a bit distracted during the game, so my performance was worse than usual. Next thing I know, the entire team started insulting me: "go to iron" "wtf phenixxx...