Because its not funny. Its a condition that has taken millions of lives and harmed even more lives related to them. Its one of those things thats just terrible to joke about, and families who have suffered as cancer victims or with cancer victims would find very offensive.
Cancer is one of those conditions that rarely sees a cure, and if it does it's not easy to cure. Because of the hopelessness surrounding life's greatest disease, it's best to avoid using it as a summoner name or insult. Now I get what you'll say, that people are too sensitive and need to man up, but cancer isn't something you can man up to. It's not something you can really fight.
Because everyone is buying into this bitch ass SJW culture being perpetuated by media and the entertainment industry. Riot, I love you but you are no different in this regard.
Cancer is a condition that takes many lives that or harmed physically or mentally the others not just to the victims but those who knew the one with cancer many joke about it but have yet to have it even interfere in their life, the person who I loved the most died to this condition and it sickens me to see that many joke about it and a majority of those who do joke about it have not be affected by the condition.