Because it has never worked for me or for anyone I know. The truth is that I dont have a hard diagnosis. Mine are caused by acidic foods and if I wanted canker sores I could get them guaranteed, if I just eat a crapload of chocolate or a pineapple or half a gallon of OJ. My doctors just tell me that you can’t get canker sores that way, which in my opinion is lazy doctoring because its a fact in my case. All I can say is that I have gotten them my entire life and nothing has reduced them, including Abreva, Acyclovir, gargling with salt water, etc., although I did take note of some of the other suggestions and will try those. But I want to repeat that the V has greatly reduced them