Quality dependable, accurate, durable rifle, easy to shoot is always in demand at a reasonable price point and the AR's meet those criteria.
Many years ago, began shooting Across the Course Matches and at that time was using an M1 Garand and then went with an M1A rifle. AR's started showing up on the firing line and much fun made of them at that time. However, when the scores started showing up for those shooting the AR's the fun making remarks became absent from those in attendance. The AR platform rifle with good barrel, quality ammunition, and with standard "iron" sights can and does deliver 1moa accuracy at the 600-yard line. In fact, have shot 600-yard matches w/ a quality AR and have produced scores as high as 597 w/ 17 X's winning the match. The Garand and the M1A/M14 rifles produce far more recoil than the AR does and that is a bonus as well. Our local range conducts XC matches on the third Sunday of each month weather permitting and having attended there for some years now see once in a while and M1A/M14 style rifle being used, almost exclusive AR shooters show up these days. Cheaper to shoot, deadly accurate in the hands of a practiced shooter, what's not to like about and AR?????