In some sense, I believe this stems from being afraid of 'not knowing'. Especially in the current SV culture, it's really anathema to say, "I don't know". "Not knowing" something is frowned upon, especially as you get deeper into your career (more senior, etc.) and it is really shameful that we have created this atmosphere for ourselves.

Being unafraid to say, "I don't know" is a really powerful skill. Now, for me, being surrounded by people who know more than I do, is actually a win. Now, "I don't know" turns into "Show me". It's an opportunity to learn and to grow.