There will be days where I do it throughout the entire match, not just when I get a kill. And then eventually all 4 players are doing it. It's just really funny to be honest. I'll do it whenever someone wastes a super, I'll do it if I want to grab some attentions, I'll do it just to do it. No harm in it.
So in those cases it just looks like they're humping the ground.
So, throw some bananas after you kill them. The banana bagging begins. JK... It's a strategy. ^_^