People creating Emps and Emps being sought after are two different things. I honestly cannot recall the last time I was in a group with an Emp though to be fair, as most of what they do is heal health and endurance its not something that is going to stick out.
I do not practice powerset discrimination, accept anyone to any group I form, and never hassle anyone about their choice in builds. But frankly, were I picking, Emp would be near the last powerset I'd invite, just ahead of Poison--too little brought to the table compared to other powerset options that were open. And heck, I'd likely invite the Poison user first just because that's a hard road to travel (having played an AR/Poison corruptor at one point).