Sometimes people speak, not to communicate anything in particular, but for all kinds of other reasons:
- Nervousness.
- Stress calming.
- A dislike or fear of silence (sedatephobia).
- To give you time to think before continuing the conversation (eg erm, so, I mean).
- As a way to unambiguously end a sentence or the conversation (eg “and that was that”, “innit”, “if you know what I mean”).
- Talking to yourself (for reassurance or to aid thinking).
- Talking in your sleep.
- Talking to pets/plants/inanimate objects.
- Talking to rehearse what to say to someone you’re about to meet.
- Filler words.
- Phatic expressions.
Probably quite a few more.
You could argue that some of those are still communicating something. But the words used and their intended meanings (or lack of) are pretty arbitrary when you look at the underlying reasons for their use in some of these examples.