An evolutionary theory of procrastination must understand that procrastination and conscientiousness have to exist in some kind of balance. There's a word for someone who does whatever they're told as soon as they are told they have to do it, and the word is “sucker”. Nearly all of the infinite number of things that it is possible for you to do would waste resources or be counter-productive. This is one reason why time management people tell you to consider long term goals, and short-term importance and urgency.
We like to think of procrastination as being yet another example of Attitude Behavior Gap. A person who is procrastinating is behaving in a way that is inconsistent with some story about how they “should” be behaving. If they themselves buy into this story, then this can be very upsetting. Not behaving in ways that you “should” behave can also have serious social consequences. Even so, we must consider that someone who “suffers” from procrastination could be acting in an adaptive way.
First, there's Social Conflict, especially individual/individual and individual/group conflict. People may come to you and say that you should do something, and even truthfully say that it would benefit the group as a whole, but at some cost to yourself. Social cooperation is overall a win/win situation, and we see it as the fundamental basis of human nature (we are the The Cultural Animal). And yet… There is still the awkward matter of your individual interest. You have been given innate motivations to protect your individual interests, and it isn't necessary for you to even be aware how those bits operate (see Intentional Opacity).
Another important way of understanding procrastination is in our theory of mind, especially the The Interpreter Theory and the The Argumentative Theory. Someone who is procrastinating is behaving in a way which they do not have a Story to justify. Perhaps this troubles them, and perhaps it doesn't, but in neither case does this lack of story necessarily prevent adaptive behavior. They are doing what they are doing. Although it is a convenient social fiction that people do things for reasons that they properly understand, that doesn't happen to be how the mind actually works. This is socially troublesome, so we have discovered moral taboos of hypocrisy and lying. But acting without generating any convincing story doesn't prevent goal-oriented behavior, it only cuts off the possibility of gaining social support.
While sometimes we may not bother to generate a story because the real story is unacceptable (individual/group conflict), it can also be useful to act without the burden of having to come up with a story. We do tend to compulsively make story about whatever we are doing as we go about our day, and this is a useful reflex–a check for whether we are about to do something socially awkward (that cannot be explained in an acceptable way.) But, aside from this peril, making story can also be a waste of time and energy, a distraction from the thing itself that you actually do choose to do (even if you can't explain why, or your explanation is lame).
Procrastination is poorly understood by psychology partly because psychology in general fails to appreciate that motivations are a distinct class of mental/behavioral entity, not at all the same as a cognitive ability or emotion. Motivations drive emotions and decide when and where you're going to use your abilities. While it is adaptive to keep your boss happy, that in itself is not going to get your genes passed on. Think of procrastination as a motivation in service of work-life balance.
We don't mean to say that procrastination is just about doing what you're told, or that it can't be a genuine problem. The point is that procrastination rests on a motivational foundation that keeps whispering in our ear “I can't believe I have to do this. There's got to be a better way.” People who hear that voice have (often enough) gotten out of doing things or found a better way. Taking a better way when it presents itself can be called “impulsivity”, at least until that other way is so well-proven that it becomes common sense.