system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do athletes spank each other?

Edit: I see alot have fallen onto the camaraderie explanation. Unfortunately, I feel unsatisfied. Why not just pats on the back?  Why not aggressively shake and rub another's head? 

I played multiple sports but I never found the need to slap anyone's ass or felt that my morale or my teams went down as a result of a lack of ass slapping. 

What are the origins?  Who first smacked their teammates ass? What have been the results of teams smacking and not smacking but instead showing another form of team chemistry?
gpt
It's a comradery thing. 

Being part of a team, there's a physicality that comes with it. You get changed in the dressing room together, you are all chummy and playful with each other. it's about keeping morale high and a tight knit group plays better together. 

By maintaining that connection via fist bumps, hi 5's (stuff people do normally) hugs & pats on the back/butt (stuff team mates do) you keep the connection going and play better as a team.