Why does no one listen to the support?

So I was in a game today, playing Janna and the match was on our side throughput the game. Then the jungler(Vi) made a call that we do Baron. Since all 5 people on the enemy team were alive at that point, I told her that it was a bad idea to go for it and that they will show up at anytime(especially the fact that their jngler was Twitch and could sneak and steal the Baron). She completely ignored me and so did the rest of the team and we went to kill it. As expected, their entire team came and killed us at the Baron pit and it costed us the game.

Why do people seem to value supports less than any other role?