In the 3025 era, the short ranges on most weapons and generally high to-hit numbers caused by those range brackets encourage you to close in unless you have Elite 'MechWarriors. Once you're in the 3-5 hex range, you might as well go all out, try to circle around behind your opponent, tuck in close, and so on.
In the 3050+ era, weapons ranges are longer and you can fit more of them (or use more of them) due to mass-lightening gear such as Endo Steel, Ferro-Fibrous, and Double Heat Sinks. This encourages you to stay at range, especially if you have Clan or more skilled pilots.