It's not about keeping spam out of comments, it's about keeping systems and content safe/operational for normal people and more costly or unavailable for the trillion dollar "AI" companies that are shitting all over everything.
Don't blame this on site operators, this is the fault of careless LLM operators knocking down everybody's walls doors and windows to "learn" from their content.
And the point of "why waste time for captcha for static file" still stands, it's not like there is comment section for bots to abuse