People want cancel culture to be real in the same way they want jews to be spreading the black plague. It lets you take reactionary measures based on false premises.
Everytime people bring up "cancel culture" they're using it as a justification for silencing an opposing viewpoint. Thats why they want it to exist, so they can justify a reaction to it.
What happens is that someone says something, then someone else criticizes them, and they try to shutdown that criticism by invoking the concept of cancel culture.
That's the part I object to. Criticism is just as valid as the initial speech and we need to protect it, doubly so when so frequently the ideas people are trying to protect are so objectively abhorrent.
I don't find the "cancel culture inconvenient to acknowledge"; I find talking about it as if it's real gives cover and justification for other antisocial and otherwise negative actions.
I cannot stress enough that telling some asshole to get out of your house and stop saying racist slurs is a perfectly norma and good social interaction that's healthy for society.