What percentage of content in your strategy should be product agnostic?

What are your opinions on this issue? Some recent talk (both online and IRL) about the goals for and approach to content marketing has sparked some questions in my mind. And looking around on discussion boards and across blogs, I really don't see this issue addressed that often: the percentage of product-agnostic content in a strategy.
Now, I understand that the customer journey plays an important role in what would be effective and what would be counterproductive in terms of the type of content that someone puts out there. But I see a great number of content pieces that seem to feel that the "value" brought to the piece is showing the benefits of a product--the enlightenment that comes from ones seeing how well a product alleviates a pain is purported to be a "value". For instance, a rudimentary example: makers of a hair trimming product publish a post about the optimal method for cutting hair. The first 1/3 is about cutting hair the regular way with scissors, and then the remainder of the post is basically a tutorial about how to cut hair with the company's product in the attempt to woo the reader by showing how darn easy it is to cut hair with the product. To me, this comes off as "salesy." This could be a good value for a current, new customer, but I find that it's rather ineffective for attractive new prospects.
In your opinion, what is the rationale behind this? Is it the desire to have an "instant gratification"? That the odd reader/viewer would bite and that is enough to deem the piece a success? Or is it something else?