I use Google Docs which has a word counter within it, but if I use it depends on the case. I do not check the word counter if I am doing my own writing. I just let the ideas flow and write as much as I can to ensure the content is as complete as possible.
In any case, editing and proofreading oftentimes reduces the final count, so I do not see much use for a counter in these use cases.
However, I use a word counter for client work to ensure I am hitting set word counts.