"I don't know." is a perfectly acceptable answer.
I've regularly encountered this in the tech industry, particularly with leaders in the tech industry. There is a false expectation that all leaders need to know everything. And once you are put in a leadership position, you must know all.
Why is this the case?
I don't know. Ha, see what I did there?
While I genuinely don't know the full reason, I do hypothesize, however, it's due to the cultural expectation put on leaders in any field. You can't possibly rise to be the leader of a company without knowing lots of things, right? Surely lots of people come to you with questions that you must know the answer to?
But I think that's the problem. Being a good leader isn't about having all of the answers. Being a good leader is about asking the right questions so the people you lead can find the answers for themselves. It's a reflection. Powerful leadership comes from having the confidence to say "I don't know.", or to ask other people for help. That's not weakness. That's strength.
And that is why I see a strength in saying "I don't know." That's admitting you don't know everything, and that you're able to see your gaps in knowledge, where to grow, and what else you have to learn. Nobody knows everything. We all have different interest, skill, and knowledge-levels. What matters is we know our deficiencies and we get help, either from other people, or by spending the time learning and growing ourselves.
This is a funny parallel to kids. I have a 10-year-old who thinks she knows everything. And I've tried to dig into why that's the case, and determine if that is a leading indicator for the future apprehension of saying "I don't know." Are we conditioned to have the expectation of all the answers? Is it that we're put in school and tested so young? Is it the pressure of standardized testing or education? I'm really curious.
But you know what, I don't know. And I'm okay with that.