Getting paid more would be nice. Ultimately, though, I think you hit the nail on the head: There's relatively few people who can take the stress of dispatch. I've been on the street as police, fire, and EMS (at different times) and I'd take that over dispatch any day. Why? Well, first responders tend to deal with one situation at a time - and in the case of a fire, these situations can last quite some time. In dispatch? You're dealing with wildly different crises every five or fewer minutes. You're dispatching police, fire, and EMS units. The lives of the people who called in AND those who you are dispatching are in your hands.
it's incredibly stressful.
And, to be honest, with the social decay in American society there are fewer and fewer felons who can take jobs requiring public trust.