Storylines. Narrative makes sports/politics/entertainment interesting, and pro wrestling is the epitome of that. People will always love heroes and villains but the layers keep them coming back. You see the good guy struggle to overcome. A good villain seems unbeatable or you itch to see them finally fall and wonder what it's going to take. You see betrayals and heroes become villains. You see friends become enemies and reunite. You see enemies reluctantly join forces to achieve a goal.
You can watch a gritty action, an emotional family drama, a romance, and a comedy in one sitting.
No re-runs. It never ends, BUT you still have to build up toward big moments several times a year to keep the crowd coming back without repeating the same exact story, so it's intriguing to see it figured out.
Live storytelling with live feedback. It's theatre...like a play, improv, dance, or spoken word but you can boo them when they suck or acknowledge them when they're killing.
Suspension of disbelief by the audience. There are rules and understandings in a contained universe regardless of the company. It's a world within itself.
Improvisation with call-backs and continuity.
Guessing where the writers/company is trying to go with stories and talent.
The satisfaction of being right.
The debates, thought, and discussion that come from being wrong.
Seeing the reaction to plans and seeing unplanned things change plans.