There are many ways to get to a blog page - Google for one, Hacker News for another. You really need some way to put it into context. Why lose the opportunity to introduce another potential user to your service?
So what you're saying, is every blog post written on a products site, needs to re-introduce the product each time? That's a fair request actually, and could be achieved as simply as an opening sentence of 'If you're new here, you might want to learn about us first! CLICK HERE'
No, I'm not saying there should be explicit text in the blog. I'm saying there should be a link somewhere on the page that takes you to the home page or "About Us" or "More about <product>". That's good design practice for any web site, because there's no telling how someone landed on your page. Finding a leaf node shouldn't leave you stranded.
