I've been playing tennis for a couple of decades and in the adult world, we generally refer our skills level using NTRP rating. 3.5, 4.0, 4.5, etc. However, since my son started playing competitively, I found out that the UTR score is a much more accurate representation of one's capability. Say, a UTR 7.2 has a very high chance of beating a UTR 5.5. And men's D1 college recruits are at least UTR 10. However, the NTRP rating isn't so clear cut. Why don't adults use UTR more?