I never saw it as anything bad. I have had people ask to be my friend on FB, and then I never hear another word from them, not one thing after six months, after a year, after two years. No postings, no messages, nothing.
I imagine other people have “fake friends” like that too and they are just trying to weed through them. It seems kind of silly to have a bunch of friends on your list (who requested to be on your list, not the other way around) that have zero interaction with you. I assume that those people were “collecting friends” in the first place.
If you weed through those people and remove them, then you don’t have to be so picky or diligent when you’re trying to post your own messages to specific people.
So I just think people are trying to clean out the unnecessary and cumbersome lists of people that they never interact with.