He is our only ball winner, he is the only option. A lot of fans feel the shift to counter attacking football is imperative for us to win trophies but we can't counter till we don't have someone who can win the ball like Coquelin does. Arteta is a top midfielder, he reads the game brilliantly and yet he doesn't have the same quality as Coquelin.
The general feeling is that Coquelin's emergence is providential and it's true to an extent but Wenger does need to be given credit too. Most young players who do not make it to the first team by the time they are Coquelin's age are sold. Wenger held onto him because he saw his unique ball winning ability.
Wenger has explained how Coquelin veered into trying to be a box to box player which kind of derailed his progress. A player with Coquelin's strengths is a huge asset, very few like him around even if he lacks in passing ability. Central midfielders who can do that are enough.