Honestly, it's started by a lot of people making the experience better for themselves. The horrible experience you can have at a live RAW doesn't really hit you until you're there. Saying what the crowd is supposed to do or saying they have "job" is weak. The show itself has a job, and that's to entertain.
We can find something we like while watching on tv, and have the ability to switch channels if we don't care for another Vickie/Divas/wrestler-you-hate portion of the show. Those people in the crowds that paid money can either sit back and be bored, or take it upon themselves to go into business for themselves.
Look no further than the Fandango song. People took something for themselves, and the E had no choice but to shamelessly play off of it by sending Fandango out there for some of the WORST segments on recent E television.
Honestly, it's just how people are choosing to embrace the fukkery that gets spun on them, especially those who want to see certain things, but are fed something else. You wanna call them smarks, nerds, wrestle fags, go on ahead. Wanna say they should just not watch then, alright. But make no mistake, shyt actually was good enough where the crowd didn't have to create the entertainment for themselves, it was done for them.
So when those start toat the next "Let's go Cena/Cena Sucks" chants, they know exactly what they're really cheering for.
Just embrace the #fukkery of it all, cuz like most things in wrestling, it won't last.

What does all that have to do with nearly ruining an actual good segment? The crowd can't go into business for itself all the damn time. And really, this is 'E, if you buy the tickets you already have an idea of what you're getting yourself into. Sometimes it's best to go in and get your mark on, save all the agenda chants and rants for the internet.