Sure but what exactly drives this psychologically? It's not that simple. For example, sometimes your character gets knocked out or killed or whatever and you have absolutely no problem with following the action for 20 minutes without having anything to do.
And sometimes I don't. Nor do some of my players.
And if you're capable of enjoying an on-going story passively, what keeps you from doing so during a game?
My mood that day, as much as anything.
Sure, boring things are boring and then people want change. But isn't that more a matter of proper staging of the combat?
Not necessarily.
Some people play 40K tournaments for countless hours over a weekend and they don't mind.
You couldn't stage a 40K combat in a way that would hold my interest. (The setting holds less than no interest for me.) So no, staging isn't everything.
I like roleplaying too. Doesn't mean I want to spend two hours playing out a conversation at the inn. I like variety in my sessions. I get bored when things linger on a particular part of play too long. Don't know why this is that difficult to accept.
In my experience this is the preference I have most commonly encountered among players. It's also my own preference. And I like variety between sessions as well as variety within the same session.