I think part of the prolem is trying to tell "how ugly is this going to get and how fast is it going to get there". There's an old saying that when seconds matter, help is only minutes away, and I can imagine that the pilot either (A) not being thrilled at the idea of mall cops swooping down the ramp on their segways in ten minutes or (B) being overly in mind of the CAD's screwup on that UA flight and at least not wanting that to happen here.