That's why introducing tougher rules is dangerous to them .... competition is increasing, and so (paying) customers have more choice. And sure, Netflix have exclusive rights to their home-grown catalog, but if they mess existing customers about too much, a proportion of those customers, especially those not desperate for that home-grown content, will vote with their feet. Or rather, subscription cash.
I don't have Netflix, but I do have a competitor. I also (lockdown aside) have spent the last dozen or so years living about 85:15 between primary and secondary home .... on different IPs. We also periodically visit elsewhere, with different IP's again. And some of that is done via a VPN. If the service I have started restricting IPs and it either meant I can't use the service as I (legally) have been, or they start making me jump through hoops satisfying them that I'm me, my reaction would not be to emulate a performing seal with their hoops, but to cancel the subscription.
Messing legitimate customers about because they think/know
some unauthorised usage goes on, in the name of hunting cash, may well end up having entirely the opposite effect to raising cash.
A friend of mine does the same as I do, and travels between primary and holiday home. One of the reasons he has Netflix is the convenience of having service wherever he is, and if that changes, Netflix would become significantly less useful to him, and so, less value for the money.
Putting in a simple code from time to time is no great problem, for legitimate users. But .... suppose I did indeed have Netflix and lent a friend an account for occassional use? He then gets "enter code". All he does is WhatsApp (or these days, Signal) me and I enter it.
If they start demanding authentication too regularly, well, we're back in the scenario of messing paying customers about for the sake of trying to block a few freeloaders. And again, risk counterproductive undesirable consequences.
And that logic even applies if they geo-lock, preventing me from VPNing, such as when on a hotel network. Mess me about, deny me the ability to use the service I pay for and I'd deny them my monthly payment ... and not be very bothered about it, due to other options.
They are,
IMHO, rather caught between the rock and a hard place and if they choose to play hardball with paying customers, some of those paying customers will decide they'll take their balls and go play with a competitor.