They can charge the next turn if circumstances permit, or the turn after that or the turn after that, or the 15th turn after having fought in melee combat for 10 rounds. Try another argument.
You never played those games where bullets have their own black holes they summon on the ground underneath them, forming a region of infinite gravitational force once their maximum range has been reached, have you? So when you aim for the head and the target is one centimeter out of range, it hits nothing (Presumably the ground, or it gets sucked into that black hole it created). Moving forward by a centimeter and firing at the same spot hits the target precisely where you aimed. It's actually pretty common in some early 21st century FPS games.
I decided to add it into this part as a gag. Obviously it makes less logical sense, but sometimes game mechanics skew the laws of the universe to entertaining results. And I do find it entertaining to imagine a bunch of horses going strong for those two spaces, however long that is in our real world units of position. Then once they reach the border of their charge range the horses suddenly brake to a stop and give a disgruntled neigh, the message being "Heck no, we carried you this far. Our union doesn't pay us to go any further than two spaces for a charge attack. Go fight in close combat you lazy human."
