I’ll answer that question for you. Yes, you do, if you’re human.
What subvocalize means is that you mentally "fill in the blanks" as you’re writing, but your reader will not be able to do the same when he or she reads it. There are many reasons that we all leave "holes" in our writing, including haste, exuberance and lack of experience.
Nonetheless, there is a cure for subvocalizing and thus making your writing understandable only to you. That cure is to leave the writing in the computer, or sitting on the table, for a day or more if you have the time. After you’ve slept on things, you’ll wake up and read your writing and realize you skipped along too hastily and left some matters unexplained or incompletely explained.
I’ve written about the ideal writing process before, but an article I stumbled upon today reminded me of the need for "curing time" in writing, so my thanks to the author of that article, Richard Kallan.