I recently spent a couple of days tracking down a problem that one of my coworkers, who built the subsystem where the bug was lurking, probably could have figured out in an hour or two at most.

Why didn’t I hand it off? Because I need to know how this subsystem works. It’s important and quite complicated and this is not going to be the last bug we have, or the last change it needs. It’s part of what I work on so I should understand it. The payoff wasn’t just fixing the bug, it was learning enough to know how to fix it.