First off, we all know who the real Herbie on the site is (me, and I was here first).
I think we've beaten this in other forums before.
When I am at my full-time place of employment (which is the busiest per capita in the nation, 130.000 jobs w/ 13 ambulances so I WIN!), we tend to treat in the ambulance, unless it is a life threat. Does that mean we just leave? NO. We tend to go in, get the patient, treat any immediate life threats, extricate, and lock everyone else out of the truck until we're ready to go to the hospital. I still stabilize on scene before I go to the hospital; I don't run to the hospital unless it's something I can't handle.
When I work in suburbia, it's different. It's all about situational awareness.