I think it's obvious that however good Best Buy is, they at best have a conflict of interest. They would like to make a sale. The sales clerk wants to make a commission. The free computer clinic is staffed by volunteers who have no financial interest whatsoever in my decision.
Now, what would you say if the city of New York enacted a law that required the free computer clinic to post signs outside saying that they did not sell computers or have experts on staff. Suppose the city blocked or restricted the rights of the free computer clinic to post advertisements for their services, or even be listed in directories? Suppose this law only affected the free computer clinic, not the Best Buy or other stores that sold computers.
Would you say that law helped me to be able to make a good decision about buying a computer?
* I have nothing against Best Buy - I just chose the name as a well known business that sells computers for my example.