For most listeners, you have maybe two seconds to get your point across before they stop listening. "Okay, you're done, it's my turn."
Modern English is carefully arranged so that nothing important or relevant can be said in two seconds.
At times, I want to talk about demand for jobs, as opposed to demand for the work those jobs produce. Except the phrase [demand for jobs] refers solely to demand for the job's work, and explaining that I want to talk about the jobs themselves takes more than two seconds. Even if I use a phrase like [demand for job openings] they're likely to stop listening between [job] and [openings]; further, pointing out their error will only make them feel stupid and turn the interaction hostile.
This is, of course, because there's lots of demand for useless cope-language, and no demand for change. E.g. there is one way to have someone listen for more than two seconds, and this is to initiate a fixed ritual. Through long practice, the cognitive demands are minimized. Listening is possible because, if you're doing it correctly, they've heard those exact words before in that exact order.. Likewise it's boring and intellectually pointless, since it's been done.
I presume that death pressure created useful language in the past. You could get someone to listen to you when they might die if they don't. Repeatedly needing language for this task, a minority of words gained useful meanings.
Opportunity cost is a foreign concept to genetic cognition, and so now it seems like not listening at all is affordable, and thus no conversationally-useful word retains a useful meaning.