Password sharing is illegal? Really?
Interesting, the screwdriver, like given the keys to do it but whether the key owner gave the keys to a third party to do something else and third party accessed content without permission from the key holder (that could be against the terms and conditions) or the key holder purposely gave them their credential and password to obtain the service for free that they haven't paid for in the keyholders name without the keyholder never being present whilst using the service.
I suppose a new answer, which I think applies to both of you, is (and it could also be classed as an analogy).
Imagine you have purchased, just ONE single train ticket, for a long (and expensive) train journey. Then you take your entire family, friends and some others, with you. Perhaps ten poeple in total. Then, as the train inspector, checks that all passengers, have the correct paid for ticket, you use a sneaky very thin (fishing line), tied to the ticket. To pass it between those same 10 passengers (cheaters), while the ticket collector (inspector), is walking down the train.
I.e. A bit like how some of the Mission Impossible Movies, trick people, sometimes, using various methods.
So, that would be (the ticket sharing), illegal. As it would be fraudulently obtaining the train journeys, without paying for most of the train fairs (apart from one of them).
I suspect, the video providers (Netflix, Amazon Prime Video etc). Could come up with techniques, to reduce or ensure, that the service(s) are used appropriately. E.g. Providing a dongle or something, which has to be plugged into the computer, or network or wi-fi (for mobile phones). In order to get the services to work.
Alternatively, perhaps that dongle (or device), needs to be connected to the particular internet network, in order to allow it to work.
Anyway, I suspect, they could come up with some kind of technical solution(s).
Where it could get complicated, is if in the one household, in the same home/address. Has three different IP addresses (because they are NOT using a land-line/broadband), but instead all using mobile network internet services. Each of which, has someone, watching the paid for, video services, on their own, individual mobile phones.