Real answer:
Psychologically, the human body and mind does strange things in order to cope with emotions.
For example, we cry at happy endings not because of "tears of joy." Children do not cry at happy endings. This is because, as adults, we have a firm grasp on reality, reactions, and predictability. We KNOW that once Neo saves Trinity's life by reaching into her and jump starting her heart, that she'll be ok.
What the tears are are suppressed feelings of anxiety, rage, sadness, and fear. When something good happens at the end of a movie, we release those tears and use the crying to cope. Once again, it's a psychological release of tension and anxiety.
Back to cancer- it's the same concept. People make fun of ANYTHING as a way to get rid of the idea that they will one day have it. The joke gets carried on in an inappropriate way that doesn't even resemble the original, and becomes a staple joke of society.
That's why people have been proven to have a fear of human-like AI.
We fear the resemblance to ourselves and the reminder that we will die. That's why cute AI don't really bother us, while the creepy babies are scary and cause anime cartoons about AI taking over to emerge.