In the tech world, it also seems to stem from insecurity (I'm sure many here have held their tongue in meetings when someone with little experience talks well above their level of competence in the subject).
Fwiw, I have the opposite perspective (maybe because I used to be one of these people!). All of the people I've worked with who go out on a limb in technical discussions and engage with their technical seniors are independent-minded and intellectually curious. Anybody can reason (albeit not as well) about a system they're working on, and a good team is able to foster this type of growth in their more junior engineers. This includes knowing ones limits, but does not include being perfect at knowing ones limits from day one.