Anyone familiar with role playing games such as Dungeons & Dragons or Pathfinder can, I'm sure, appreciate seeing an actual image of the character they've put so much time and thought into.
As a personal fan of such games, I can certainly vouch for the added flavor an illustration of a tabletop RP character. While it may not lend any particular benefit when actually playing outside of perhaps helping your fellow players have a better understanding of your character's appearance, the connection between a player and their in-game avatar can be important. As such, helping them develop a character in such a way is more than just a fun thing to draw.
Seen here are a few examples of this; player's original characters from a number of games including D&D, Pathfinder, and a number from a Marvel-based RP. All were created based on the players' descriptions, whether highly-detailed or just rough ideas.