When I'm gliding cross-country and I'm close to an ATZ, I'll often tune in to the freq as it obviously helps to build up a picture of what is going on in the local area - particularly if it's midweek and I'm near a military airfield with a VHF freq.
However, unless I'm contemplating landing at the said airfield I never transmit to advertise my presence. This is because over the years I have become completely disenchanted with the lack of understanding of ATC units concerning gliding. Being asked to maintain an altitude is ridiculous enough, but years ago I was once asked to climb! (I asked for a radar vector to the nearest decent thermal!). Beside which, the less time I'm fiddling with avionics, whether it is GPS or radio, the less time I am looking out!
Most of the time, and especially if I'm getting low, I have the radio turned down or off. The R/T discipline on the UK gliding freqs is appalling and one of the reasons I love my gliding is the occasional peace and quiet away from the rest of the family is part of the attraction.
Hope this view helps put glider pilots' use of radio into perspective.