The reason was probably that no one ever needs to delete just a subset of cookies from a site. I certainly never have, and I'm a pretty technically-minded user. (Other than for development, in which case I'm using dev tools anyway.)
Counterpoint: I've many times had to fix presentation of or access to a site by purging just specific cookies. Two sites that have previously had these problems are RingCentral's web interface and AutoTask. Maybe a dozen or more others, but admittedly not many…however, when I've needed it, the problem has been persistent, requiring multiple fixes per day, over a few consecutive days or or even a couple weeks.
Is it? I feel like most of my atrocious cookie hand fix cases end up being broken redirects where you get redirected to some new url that errors, so loading the page doesn't help to get rid of the offending cookie.
That would be an atrocious bit of engineering from the developer. But I suspect that even in that case, holding Escape as you load the page would kill the redirect.
Not who you were responding to, but I've had that happen on Microsoft flows.
Manually interrupting most flows is practically impossible. Too fast, and can chain across a half dozen (sub)domains near instantly. The web hasn't been that slow or simple in a long time.
