Why are tubeless tyres popular in mountain biking?
Although this is purely anecdotal, I know from my own experience mountain biking that most of my flats were from so-called "pinch flats" (where the tube is pierced by pinching or friction with the tire/rim rather than piercing by an external object). This was highly annoying. After having switched to tubeless some years ago, I've not yet had a single flat. And, obviously, without a tube to get pinched, there's no way to get a "pinch flat".