You'd think so. And yet, here we are, nearly a half-century into D&D's dominance, and I think it's still so popular not despite the relative lack of mechanics for doing anything outside of combat, but because of that.
Not trying to get us into the pointless old debates about D&D's bugs, features, and bug-features, though. I'm just stubbornly trying to circle back to an earlier point, that there are tons and tons of games with very cool mechanics for social interactions and other non-combat stuff that might come into play in SF and any genre that isn't D&D (which is its own genre, related to but separate from high fantasy, in my opinion). Those systems don't require you to invent and graft on rules for not killing things. Some have even thought through all kinds of apparently thorny issues, like how to reconcile high-tech weapons with overall challenge levels, or this odd business that keeps coming up in this thread--the problem of ship-scale weapons vs. kaiju enemies, a gripe that's so firmly planted in D&D-centric FIGHT THE MONSTERS WITH WEAPONS THAT'S ALL THERE IS TO DO IN RPGS play-style I feel like I'm in an entirely different hobby. Those other games are just sitting there, waiting to be played.