Why? Your legacy depends on it, and since this is a Christian site, I'll just throw in that the future of the church depends on it. For centuries Christian leaders were generally grown through mentoring. That isn't as true anymore as it was in the centuries that produced Polycarp, Luther, Carey, and others. Yes, of course it's true that not all Christian leaders were mentored into their jobs (Carey was a cobbler's protege). But that is actually the fact that makes mentoring all the more important. Do we want to wait until the church has to hope for the next Calvin? Or do we mentor to find him? I would suggest that the latter is the best option.
Pastor, if you don't currently have a protege, then you are wrong. Fix this immediately.