Maybe a lot of players instantly respawn, I know I usually I do, because I've learned no one's coming to help me. But I'm surprised by how many players I see who will wait to be revived. I may be a ways away from them, and I fully expect them to poof before I can get to them, but usually, I can make it. I think those are the players who understand how important it is to be revived vs have to travel all the way back to the objective, and so they try and wait for revival, and usually, if I don't do it, no one else will. So I try to help them.
I revive less than I used to, especially when not on a Sunflower or Scientist, but if I can revive someone and I don't think they're just going to get gunned down right after they get up, and I noticed we get a rainbow invulnerability effect in BfN, I will usually try. It's enormously useful with the longer run distances and once we get team vanquish, it can be the factor that turns a close loss into a victory.
