I think that's a bit harsh - like it or not, gliders, like some microlights, paragliders etc, DO have much better provision for keeping a good lookout.
Also, gliders, like other soaring aircraft, spend a fair bit of time flying at close quarters with other aircraft, so their pilots tend to be more aware of keeping a CONSTANT good lookout.
This isn't a criticism of other aviators, it's simple fact.
I've flown many different types and know full well that visibility varies enormously. I never, ever, felt wholly comfortable flying under VFR in a twin turbo prop, for example, as the "letterbox" view out always made me feel as if I was missing the view of so much of the sky. Flying a glider, or flexwing microlight, has conditioned me to appreciate the virtues of good cockpit visibility and also understand the vulnerability of flying something slow and light in the presence of heavier stuff.
Whatever the AAIB outcome, we can conclude that two aircraft colliding in Class G is very likely to have had an element of poor lookout as a causal factor.
VP