Um, what?
The fourth wall
The crowd used to be an interactive element that wrestlers would draw from, much like the crowd of a real sporting event. Nearly all interactivity between wrestlers and crowds seems to have ceased, though. In essence, WWE wrestling has moved behind a fourth wall, becoming not much different than a sitcom ('Taped in front of a live studio audience.") where wrestlers and other WWE characters only acknowledge other wrestlers/characters and ignore the audience.
That doesn't necessarily apply to just promos/"sketches" either, but also in matches. I remember a couple years back when Hogan was in-between WWE stints and would talk about how in his matches with newer wrestlers like Lesnar, the wrestlers would adamantly stick to the script, rather than realizing what the crowd liked and deviating to run with that instead.