Errr, first of all you mention Focus action. That by itself is a 'penalty'. To increase the range you have to spend an AP (to aim or focus on spell casting or whatever).
As well as argue about how probable/improbable it is to hit a target at 15 or 30 meters you could start to question the lethality of attack a vs attack b.
Also, have you ever tried to draw, aim and shoot in the same movement? A target too close, that also move might actually be harder to hit than the same moving target further away, simply by the fact that you have to move the barrel of the gun further to keep it ained at the target.
However, all this is beside the point. This is a game and a game have to to some degree be balanced. As it stand currently the game is rather balanced between shooting and melee (some exceptions ofc) and to introduce "more realistic rules for shooting" (in a game that have magic, risen corpses, angry mini-dragons and green rednecks) would shift that balance. Different games have different rule sets and different ways to score a winning game. This is Malifaux, we shoot from the hip, have gremlins and mindless zombies.