Why I don't write four books a year

Last month, there was an article on Huffington Post asking authors not to write four books a year. I am happy to say that I don't write four books a year. It's an accomplishment if I can finish one novel a year.

Do I write just one novel a year because I agree with the article and think that a good book can't be written in three months? Do I believe that any book that doesn't require a year's worth of work must not be very good? While I do work hard on my books and try to write the best story...