[vouaobrasil]

I disagree. One can also want to write more as an end itself, simply to become a better writer.

[quanticle]

    I disagree. One can also want to write more as an end itself, simply to
    become a better writer.

You've contradicted yourself. Writing to become a better writer is a goal that's different than writing as an end in itself. Moreover, writing just for the sake of writing is not a very good way to become a better writer. Using word count goals to improve one's writing is like counting the number of times you kick a ball each day and using that as a measure of your progress as a soccer player.

[john_the_writer]

Well, that would be a measure.

The number of lay-ups you do each day as a measure of basketball.

The number of miles run as the measure of my ability to finish a marathon.

As you write, you'd become better at getting ideas out of your head. Regardless of the grammar/vocabulary. You would be better at the act.