In most cases, the content supplied by some of these services has been used on many web sites already. Sometimes it's been rewritten slightly, but the content is the same. "Content Mills" obtain the content from a variety of sources, some of them perfectly legal. But that content may have originated long ago and be out of date. Worse, your customers may have already seen the same material on another web site, even on a competitor's web site.
When you buy web site content from a professional web content writer, you can be sure that it's original, fresh, and tailored for your web site alone. It's a little more expensive, but the payoff in customer approval is more than worth the small additional cost. There's no substitute for custom content for your web site or blog. It makes your site stand out from the crowd, rather than blending in with the mass of other websites that are competing for your customers.
Email Me for a free evaluation of your blog or web site content. I'll make recommendations of how custom content can add new dimensions to your site.