Yeah, LV and NYC convention sites are probably the worst/most-obvious examples.
Plenty of stories of presenters being disallowed from plugging in their own equipment without a union employee there to assist and other things like that.
The worst I heard, was one of our sales reps (a woman) came in, with a "weekender" purse (big purse). She was stopped at the door, and wasn't allowed to enter the main hall, for about five minutes, until someone was called over, with one of those huge, hydraulic skateboards they use for moving big furniture.
They put her purse onto the center of the cart, and escorted her to the booth. Then, they got upset she only tipped one guy $5.
I know these are "one-off" stories (and she probably gave attitude), but there's so many of these anecdotes, that it causes huge damage.
I think the problem is that the fast majority of workers in the US would probably have better work conditions, job security, or compensation if they were in a good union. So on one hand we have an extremely niche union that sucks, but also however many hundreds of millions of Americans as the other example of why unions are needed.
The problem with pulling this crap at convention centers, is that the people that they are pissing off, are the exact people that they want on the side of the union.
Plenty of stories of presenters being disallowed from plugging in their own equipment without a union employee there to assist and other things like that.