Those events highlight the spooky power of Anton Chigurh. It displays how adept he is and we don't need to go into the details, that's not what the film is about.

It seems you're a bit mislead about the expositive power of the film which actually comes from the novel. If you're a fan of McCarthy you can see the difference between the visualization in Blood Meridian and No Country. He goes into some detail about hiding the money in the heating vent, in fact that's when I realized he had written the novel to be a film. And sure enough, a couple of years later the Coens were shopping it, and I believe he wrote it for them to make into a film. None of that is specifically known, McCarthy doesn't do interviews much, or really at all.

He has written a play, though. His command of what is and is not stated is absolute. There is nothing missing from the novel, and the Coens miss nothing.

Those answers are not there because they do not need to be there. It doesn't advance the story, tell us anything about Anton or Llewelyn, and so they are not explained. It's economy. The Coens and McCarthy are particularly suited for each other in this regard.

OTOH, the film faithfully reproduces the hiding the money in the vents sequence? Why? It tells us something about Llwelyn, it explains position in the Motel (a more important facet in the novel but still explained in the film.)

I generally hate that "well it's Shakespeare so it's you that missed" type of answer but we are talking about McCarthy and the Coens, here. The real question in how you view film is why you need to have answers to those questions? If the answers aren't given, then where should you be looking?