Surely that cannot be a reason pilots actually cite- "Better to risk a collision than to sit the exam for FRTOL"????
I doubt there are a lot of gliders that reason this way. In fact, I doubt that there are a lot of glider pilots that know that there are ATSOCAS services available to them anyway. In general, I think their belief is that you only need the FRTOL if you want to pass through controlled airspace - which they rarely do.
Furthermore, the reality is that a lot of gliders *will* use the radio during their soaring flights. But they're on one of those dedicated glider frequencies and they will use it to keep each other updated on where the lift is, what altitude they're circling and so forth. Even if they wanted to (and were allowed to) talk to a LARS unit, they would need to switch to the LARS frequency and would be missing out important, possibly vital information from their fellow gliders. And no, a typical glider does not have the kit to monitor two frequencies at once.
All that, of course, apart from the distraction that this may cause. Which might be a reason for a glider pilot to switch off his radio altogether and rely on the Mk. 1 eyeball alone.
I'm not defending the glider community here. But I am dipping my toe into their waters (with a bit of luck and planning I should be able to get my GPL this summer) and I find that gliders have a completely different attitude towards radio, transponders and a few other things that power pilots simply take for granted.