All the procrastinators are here so here's my most recent thinking on the subject: Procrastination is just an emergent behavior of the "human runtime executive".

Consider first a cat: it sleeps (in the warmest place it can find, but not too hot) until it is either hungry or bored or someone shows up to amuse it. Then it hunts prey, plays with it, possibly eats it. Repeat.

I believe the human (at least male human) version of this algorithm is roughly: sleep when tired, otherwise absent some imminent threat (see below) work on various plans directed toward having sex in the future, otherwise go figure out the world. Imminent threats (hunger, leaking roof, dangerous predators, "sprint" deadlines...) trigger immediate and focused activity.

I think this explains procrastination and pretty much everything else: doing things like the VPTree implementation doesn't rise to the level of dealing with an imminent threat (unless someone needs to ship it in a product tomorrow), and it doesn't fall into the category of "figure out the world" because you already know how said trees work and are used well enough. And of course it isn't terribly sexy, most of the time.