Do the folk who ask you if you've done the BGR know you enjoy the long challenge-type events prior to asking if you've done the round John?
Having spent a spring and summer training on the fells it's interesting that the BGR is very much on the radar in Lakeland. This seems a local thing up there. If you're running in the Peak, Dales or Pennines you're much less likely to be asked if you've done a BG. It's actually one of the many good things about training for a round. You become surrounded by it and cannot help becoming absorbed into it
40,000 people a year 'run' the London marathon. Roughly 1500 have done a BG, ever. I suspect it'll not become just something to be ticked as it's just too hard