This is such a weird take. I mean, either I am sharing the bill (I'm not), and the cutting off is rising my price or I... you know, actually like the person using the sub when I'm not and I'm still mad that they are getting cut off. Plus who's to say I'm the primary user? For all I know I'm in there way less than the other person.
It's weird to assume that I would only be annoyed at my own inconvenience and not by the inconvenience of someone else. Plus in practice the outcome would have to be paying their cut-down "second account" nonsense and paying more myself, it'd be kinda petty otherwise.