The idea being the user(s) would then have to share a email inbox to share logins, not just a password. It might not be the most inconvenient - this is partly how Netflix did their "Household" lockdown. You can request a travel code and this gets emailed to the primary email.
I feel the way Netflix did this broke the social contract of profile sharing on purpose - before, if you were a good tenant, you could freeload off another paid account without inconveniencing them at all. Memes and jokes formed of still being on an ex-partner's account or how people would rename themselves "Settings".
Getting an email and being harassed for the code by all those account sharers? Much more open and open for annoyingness.
