I think also that glider pilots have superior look out in general because they have superior vis. Looking around maybe 270 degrees in a glider with almost clear vertical vis from zenith to ground is a lot easier than a spam can. In fact the view is very limited from the average spammy.
I say superior look out in general because unless you're going to make use of the superior vis it may as well not be there. I've had more close calls in gliders with other gliders than in spammies. Glider pilots are not immune from poor lookout, in fact I would say that spam drivers try that bit extra because the lookout is so limited.