There is probably a bit of health & safety rules and fear of litigation coming into play, I don't know the rules for UAS but a few years back at a fly-in in Aberdeenshire I offered 4 ATC cadets a ride round the pattern, all accepted and I gave them control on the downwind which they loved. Fast forward to last year and a different group of cadets did a fine job giving Lt.Cdr. Jock Moffat (Sink the Bismarck) a welcoming parade at Scone for an award he was receiving. Afterwards I offered them the same thing but the leader said they weren't able to accept due to risk and liability. Shame really but that's the world we live in.
Edit to add: The Aberdeenshire cadets had all done glider training and really knew their stuff, 3 of the 4 were girls and two of them were originally from Eastern Europe, all well disciplined and professional, a real credit to their squadron.