It differentiates human-created content from AI-created content in a space where AI can’t perform competitively at all. So, just as with Crunchyroll, better to kill the complex human artistic subtitles so that people don’t get used to their boring “could be machine, could be human, who cares” slop (and, as a bonus, so that human moderators aren’t required to evaluate whether the subtitles are offensively shaped).

They still support multiple formats with color information

I mean, it’s sort of a vector. The malware itself can only be executed if you click a suspicious .lnk file. The moral here isn’t that subtitles are a “vector”, but to not indiscriminately run scripts.

Is it pointless? I find myself asking for summaries of videos more and more often.

They aren't useless, it's nice for finding timestamps of things, especially in long content like talks.