Have you ever read or posted something on a message board to find multiple people strongly posting an opinion? They may be correct from their experience, but there is a possibility they may be victims of conformation bias.
This type of bias happens often at hair loss message boards. Someone will ask a question such as "are there any other treatments that work outside of the big 3." Then, there will be a few loud vocal commentators who will confidently proclaim that there is nothing else that works. This echo chamber creates a perception to the outside viewer that nothing has changed in the world since 1990.
These echo chambers, or false opinions repeated loudly, create an environment of confirmation bias. This is the tendency for information to be interpreted in a way that confirms one's existing beliefs. People then, under a false notion, think that no other product can work.