My understanding is there are takeoff and landing qualified pilots at the field with line of site that take care of departures and arrivals. Sometime after departure they hand off control to the crews at Creech, or wherever else the ops are controlled out of. I believe there was enough latency in the satellite based control from the other side of the globe to be “problematic” during takeoff and landings. It wasn’t uncommon for them to step on radio comms in an air stack over an op for the same latency reasons.
This Air Force fact sheet makes mention of it:
https://www.af.mil/About-Us/Fact-Sheets/Display/article/104469/mq-1b-predator/
I know it’s for the Predator but I would imagine Reapers have a similar limitation. My info could be dated though.