Would you disagree that, by page or word count, the rules are predominantly about combat?
Might be that many rules cover combat but still, I would disagree based on that D&D is a RPG, a Role Playing Game, not a CSG a Combat Simulation Game.
I do agree, that the mechanical aids for role playing situations are less than in other RPGs, but ideally you would not have to use these much, other than if in a social interaction some player tries something extraordinary, or some player wants to do a social interaction but is not that fond of roleplaying it, therefore only describing what he likes to do. Still the tools are there, whether there could be more or not.
Just that many people do not use the role playing part of the game and others do, does not change that. The eight encounter / day suggestion enforced that, some people seem to think, that that is all, that D&D is about. But the best games imho, are those, where multiple solutions to some situation are possible, one of these well migh be combat.