Ask HN: how important is it to be an expert in something?

when I read job postings for the latest hot tech startup, or read profiles of big name programmers working at these startups, it seems like being an expert at something is a necessity to make it (and in some cases, an expert at multiple things).

I've been programming professionally for a few years now, and I don't feel like an expert at anything. I don't know if it's because of the environment I'm in or that my "expertise" thinly spread across coding what I code and the industry/domain I'm in.

I guess I'm sort of a jack-of-many-trades, but truly an expert at none. I know startups often say they need generalists, but it also seems like a startup needs people that are really, really good at many things to get a startup off the ground.

should I be spending my weekends consciously trying to become an expert at something, even if it's not something I'm going to use/reinforce in my daily work? or is depth overrated compared to breadth?