Okay, I'm going to argue that it's not rampant. Is it there? Sure. Rampant, probably not.
A few points that seem on topic:
1) The game design promotes combat effectiveness. Pretty much every ability is designed in terms of combat power, except for, as described in Unearthed Arcana articles (and maybe the DMG), the things known as 'ribbons'. Ribbons are called out as being ignored when it comes to balancing class power.
2) Combat is actually predictable. Roleplaying is not. This is of major importance when writing an adventure you want to have a set length (such as a 4 hour convention slot).
3) Fuzzy logic goals are just that - fuzzy. Combat goals are simple. That means that RP XP is much more difficult to award consistently, even if you assign goals for it, particularly the more complex you make it. Combat XP just scales with difficulty.
4) Is min-maxxed combat necessarily a bad thing? If combats are shorter, doesn't that allow for more RPing time, in theory?
4b)How well does that theory hold up? Does shorter combat equal more RP time or longer lunch break?
5) Why is everyone playing the game? Not everyone plays to tell in-depth, personalized stories. Some people are, in fact, playing because being a murder-hobo IRL results in Suicide by Cop.