> A general behavior I observe in colleagues or co-workers is that they highlight half of a paper, but they never do anything with that highlights.

They might be using this exercise to help them focus and absorb what's important on their first pass of reading -- they might not expect anyone to ever use their highlights.

People will have been taught different techniques, and adapted their own.

I never got into highlighters. We were taught to keep our books unmarked, for the next year to reuse them, or for resale value.

In grad school, I was told paper-reading techniques closer to what you describe.

(Skim abstract, decide whether to keep reading, skim results/conclusions, decide whether to keep reading, look at citations, cynical joke about citation politics, decide whether to keep reading, then some order of skimming introduction and related work and other parts that I don't recall because I didn't follow that guidance, and then eventually you might give the whole thing a close read.)