I've often thought about doing this. But I always end up coming back to the question: do I want to spend a month (or more) writing a blogging engine, or do I instead want to focus on my actual writing? And what will a custom engine actually give me, aside from sleepless nights and headaches?

Jekyll is a great answer in this regard. You don't have to reinvent the wheel (pagination, RSS, categories, dates, etc.), but you can still customize it with great ease. (Kind of like the Backbone.js of blogging engines, I guess.)

Some people probably don't find blogging platforms all that interesting and would really rather just say what they have to say and get back to whatever else they were working on. If someone asked me what's a good kitchen knife, I wouldn't say, "make your own" (even if that's what I would rather do).

Fair, but I think most of the things being suggested here are open source, so the truly curious can use them as a starting point.

Alternatively: it's good to see what's out there so that when you do (inevitably) write your own, you know /what you want/.

Don't be; I came to the comments section to suggest rolling your own. You are, after all, a programmer.

...although I might not've hit submit, since I'm not sure I'd want to participate in the argument that'd be sure to come next.

TIL what TIL means. You are too lazy to type "Today I Learned" and your answer to someone asking for a blog platform is to build it themselves?