You see this with the viewpoint of a character who most likely will win in a melee combat action.
But considering that melee combat in A!C (as in STA and others) is a struggle, an opposed action, it is risky for the attacker. That is the material point of difference.
If you shoot at someone, you usually won’t get shot back right away (though there are some Reactions, especially in Infinity, where this will happen - a carry-over from the ARO’s of the miniature game).
But if you go toe to toe with someone in melee combat, the chances are that one of you will get hurt - a tie is quite unlikely (though might happen).
That is to be taken into account for PCs engaging in melee attacks. They will be in a higher risk situation. And considering that their opponent might not be a mob of minion troopers, but a more worthy opponent, this is actually a very dangerous tactic.
A melee-optimized character will often prevail, winning as the attacked character and maybe attacking some other opponent by themselves and winning the second opposed roll, too. But in defense as well as in offense there is a high risk - and the GM might raise this a bit by buying additional dice or activating some Truths that make things even less likely to go in favor of the PC.
Shooting someone from a distance is a bit more difficult depending on weapon, range, visibility of the target, but much safer.
Regarding Reactions: there is only ONE Reaction (without a Talent) in A!C, which is Hit the Dirt. And you can only take a SINGLE Reaction per round anyway.
That is totally different to the way Conan or Infinity handles things, where you can take as many Reactions as you like, paying more Threat for each Reaction.
To introduce a Melee Reaction would mean that either the Melee defense is the ONLY Reaction the character could take this round - so the next melee attacker would not face any risk of getting injured at all. Or you introduce more than one Reaction, which will cause the whole action economy for NPCs to topple.
A!C GMs don’t need to spend any Threat for their often melee-oriented monsters on the defense in melee combat. In Conan the GM is often hard pressed to keep sufficient Doom to allow the NPCs their Reactions, this was solved quite nicely in STA and A!C by making Melee combat an opposed roll anyway - no additional Resource costs, no Reaction needed.
As I said, if you haven’t tried A!C’s combat system in an actual game, you will be in for quite some “surprises” how things won’t work anymore, if you tinker at this crucial spot in the combat system.
Of course, maybe you are lucky, maybe your players find that acceptable, but I wouldn’t count on it.
If you really want the melee combat handled in the way of Conan or Infinity, I recommend taking the Infinity combat system, which is geared towards more modern weapons (fire rate, etc., too technologically advanced for Conan). This works fine, but it is VERY different from the A!C system. - So still a lot of work to make it run in A!C.
