Donald Maass listed action scenes and sex scenes as scenes people skim. Part of this has to do with tension, and heightening the tension and pacing it. Part of it has to do with the expected nature of what unfolds.
I have a process for sex scenes. I write them, and about half way through I decide it stinks and I don't want to go on and I force myself to finish. Next, I read it and cut about 3/4 of the action out. Then I read it again and put other action and some thoughts back in. And usually a finally round of edits for ease of reading language.
But action. UGH.
Those are big battle scenes that we can't model quite so accurately off our real lives. I have sex, but I don't often slay villains or sacrifice young girls to pagan gods.
It's part imagination, part physics, and part creative editing so you don't provide every detail but enough to keep the reader informed and interested.
And lots of danger. I'm working on a big scene right now and there will be more on this when I finally get it right... because right now... it's not