Thanks, rural East Lothian, a beautiful place.
They were once quite common on mtbs, but I think that was when narrower completely flat bars were the norm, since the move to wider riser bars, they have been less common. Maybe because the position on a modern mtb is much more upright (especially the full suss bikes), so the bar end does not seem to be such a natural way to hold the bars anymore, or just as you mention, bar ends can catch on things that they shouldn't. All I know is my first fully rigid mtb had bar ends and I used them alot, but neither of my two mtbs now have them, and I don't miss them, perhaps I'm just a fashion victim