Because we expect ourselves to be perfect.
Procrastination and perfectionism often go hand in hand. Perfectionists tend to procrastinate because they expect so much of themselves, and they are scared about whether or not they can meet those high standards. Perfectionists sometimes think that it is better to give a half-hearted effort and maintain the belief that they could have written a great paper, than to give a full effort and risk writing a mediocre paper.
Procrastinating guarantees failure, but it helps perfectionists maintain their belief that they could have excelled if they had tried harder. Another pitfall for perfectionists is that they tend to ignore progress toward a goal. As long as the writing project is incomplete, they feel as though they aren’t getting anywhere, rather than recognizing that each paragraph moves them closer to a finished product.
Because we don’t like our writing.
You may procrastinate on writing because you don’t like to re-read what you have written; you hate writing a first draft and then being forced to evaluate it, in all its imperfection. By procrastinating, you ensure that you don’t have time to read over your work, thus avoiding that uncomfortable moment.
Because we’re too busy.
Practical concerns: jobs, other classes, etc.
Because it works.
Unfortunately, procrastination helps reinforce itself. When we avoid doing something we dread (like writing) by doing something we enjoy (such as watching TV, hanging out with friends, etc.), we escape the dreaded task. Given such a choice, it’s no wonder that many of us choose to procrastinate. When we write a paper at the last minute and still manage to get a good grade, we feel all the more compelled to procrastinate next time around.