Article: BYU has 21 NCAA varsity teams. Nineteen of these teams played mainly in the Mountain West Conference from its inception in 1999 until the school left that conference in 2011. Prior to that time BYU teams competed in the Western Athletic Conference. All teams are named the "Cougars", and Cosmo the Cougar has been the school's mascot since 1953. The school's fight song is the Cougar Fight Song. Because many of its players serve on full-time missions for two years (men when they're 18, women when 19), BYU athletes are often older on average than other schools' players. The NCAA allows students to serve missions for two years without subtracting that time from their eligibility period. This has caused minor controversy, but is largely recognized as not lending the school any significant advantage, since players receive no athletic and little physical training during their missions. BYU has also received attention from sports networks for refusal to play games on Sunday, as well as expelling players due to honor code violations. Beginning in the 2011 season, BYU football competes in college football as an independent. In addition, most other sports now compete in the West Coast Conference. Teams in swimming and diving and indoor track and field for both men and women joined the men's volleyball program in the Mountain Pacific Sports Federation. For outdoor track and field, the Cougars became an Independent. Softball returned to the Western Athletic Conference, but spent only one season in the WAC; the team moved to the Pacific Coast Softball Conference after the 2012 season. The softball program may move again after the 2013 season; the July 2013 return of Pacific to the WCC will enable that conference to add softball as an official sport.

Question: Why are many BYU athletes older than other schools' players?
many of its players serve on full-time missions for two years