It's not just that. we're emotional beings and we form emotions around food at an early age. We form deep intrinsic bonds to certain things and it's hard to disconnect. When someone deeply ingrained in the meat based or heavily processed side of the S.A.D is in the process of going vegan it can be beneficial to occasionally allow yourself to eat something that is comforting before you say goodbye to it forever. Putting too rigid a definition on veganism turns people off from the lifestyle. The original definition of veganism is and always will be

"Veganism is a way of living which seeks to exclude, as far as is possible and practicable, all forms of exploitation of, and cruelty to, animals for food, clothing or any other purpose."