The Ground Control Stations (GCS), or "desks" as some uninformed insist on calling them, can get FOD'd with non-approved flying clothing creating control restrictions and loose clothing/jumpers can snag switches and controls. Don't forget that crew changes are frequent with individuals climbing in and out of the seats. The GCS are chocker with lots of electrical equipment that can catch fire and the only exit is to go past this equipment.
So, yes, they do wear flying suits, for obvious reasons.
What a bunch of b*****s! Airline pilots quite happily fly in nor mal rig so why not UAV "pilots". It is nothing more that a SOP to the Air Force angst that you are not a pilot unless you are in a flying suit. Same thing happens at the non-flight Air Warfare Course at Cranwell - pathetic.