When I specifically get paid to do content writing I do not have any control over the topic and SEO is important.
On Hubpages I do have control over what I write. So I choose to write about subjects that I care about. So up to this points all of my hubs have been about music, because when I was younger there was part of me that always wanted to be music journalist. I am very passionate and knowledgeable about music. At times the specific music topics may not always be the most marketable topic. But I view hubpages as an outlet to write about subjects that I am genuinely interested in.
That being said there are certain SEO tips that I still try to employ in my hubs. If I can make a little extra income writing about things I love, that is always a bonus. But I don't focus on SEO to the point that it will compromise the integrity of my writing.