Articles are written and offered for publishing and distribution by the customers. Customers name and website address is mentioned in the articles. So the content of the articles represent the reputation of the customers. Even search engine knows that there is relation between the site getting the links and article writer.
In Guest blog writing we do not show that there is any relation between the website owner who got the links and the blogger. Content of the blogs has no direct relation with the customers whose link is given so the reputation of the customer is not at stake. Further Blogger are from different culture, society , caste or region and they are from different part (Location) of the world so nobody can say that it is written by the link owner. For example in Bespoke links, content are written by the site owner not by our customers. Similarly blog content are written by different blogger.