I'm afraid you need to go into specifics.[MENTION=12731]CapnZapp[/MENTION] I still feel that your argument that D&D favours moving to close in to melee rather than using cover feels more like theory crafting than actual gameplay practice. But even conceding that it might occur in standard D&D, I still don't see that it will be a factor in a Western setting.
In a Western setting, ranged combat is king. Your primary damage dealers are pistols and rifles and shotguns, with things like knives and tomahawks coming in second and also being throwable.
So, in this setting, where's the motivation to charge into melee? What purpose is there in a character running around in the open? Sure, the HP model may somewhat mitigate the downside of such a tactic, but what's the upside? Why wouldn't people make tactical use of range and cover in those circumstances?
As long as we just take "ranged combat is king" for granted, sure enough, there's little motivation to charge into melee.
But how to accomplish the change?
I'm sure you agree D&D as written is very much a game with prolific motivation to charge into melee. Something needs to change. And that something is crucial to giving an answer.