Comment by ndriscoll

I've always encouraged everyone more junior to review everything regardless of who signs off, and even if you don't understand what's going on/why something was done in a particular way, to not be shy to leave comments asking for clarification. Reviewing others' work is a fantastic way to learn. At a lower level, do it selfishly.

If you're aiming for a higher level, you also need to review work. If you're leading a team or above (or want to be), I assume you'll be doing a lot of reviewing of code, design docs, etc. If you're judged on the effectiveness of the team, reviews are maybe not an explicit part of some ladder doc, but they're going to be part of boosting that effectiveness.