So what is it that drives such phrases into common parlance as a description of the apparently-fictitious culture of rote cancellation, might one suppose?

I might suggest that "projection" is a primary motivator, although I work to avoid projecting on my own time.

(Edit: To disambiguate without vagueness: When some fucking party or other is talking about "cancel culture," they usually seem, to me, to be projecting about their own fucking party's fucking ugly policies and tactics.

And in a sane and pure world, I'd like to wish that they'd be recognized as being fucking scumbags for behaving in this way.

But it is my observation that we do not always live in a sane and pure world.)