Euuuwwwww....What's That Smell?!?!?

What is it that is so fun and enjoyable about spending time in a stinky room breathing sticky, smelly air saturated with the moisture of human sweat? What is it that we love about rolling around on the ground with people trying to incapacitate each other? Is this the closest we can come to a primal force and to experience the (relatively safe) struggle for survival? Or is it a regression to the playful innocence of free movement that we see in nature like tiger and bear cubs playing. Who hasn't heard the analogy of a new jiu-jitsu parent comparing their new baby's movement to the movements and positions of grappling? Is this stuff we all knew once before but have forgotten in our "development" or "growing up"?
What is the comraderie that comes out of this communal primordial ooze? What is the bond that happens between people that voluntarily and repeatedly put themselves through the physical and mental struggle of learning and survival...day in and day out, year in and year out? What makes one person stop coming in and another keep returning? What makes a person come back after taking several years off? What does this activity provide that even with all the injuries, pains, sweat and infections keeps us going back?
Is it about escapism? It's a place where you have to be so focused on your own survival that you don't have the luxury of thinking about what happened with your boss at your job or the fight you just had with your wife/husband, boyfriend/girlfriend. It's a place where the rest of the world melts away and ceases to exist. All that exists is what is in front of you...or behind you or around your neck or pulling forcefully on your arm...