In 2013, the NFL passed a safety rule that allows each NFL team just one helmet over the course of a season. Believing that the changing of helmets leaves players more prone to head injuries, the league instituted the policy to protect its athletes. In the process, it left individual franchises unable to roll out the alternate and throwback designs running rampant in college football as frequently as they would like.
While the decals of that one helmet can be removed and changed out with others, a single helmet color can be difficult to pair with various uniform color schemes.