Because the problem's not just with landline but with any direct-dialed PSTN telecoms system. I don't want a landline or mobile phone any more. The situation's well past simple cord-cutting.
It's been about three years since I stumbled across this quote which confirms that at least someone on the inside is aware that the present situation is eroding all trust in the system, and that this is an existential threat:
[S]ince mid-2015, a consortium of engineers from phone carriers and others in the telecom industry have worked on a way to [stop call-spoofing], worried that spam phone calls could eventually endanger the whole system. “We’re getting to the point where nobody trusts the phone network,” says Jim McEachern, principal technologist at the Alliance for Telecommunications Industry Solutions (ATIS.) “When they stop trusting the phone network, they stop using it.”
https://nymag.com/intelligencer/2018/05/how-to-stop-spam-rob...
(From an earlier HN comment of mine: https://news.ycombinator.com/item?id=21542926
Stir-Shake may have reduced levels of spam, I've no way of knowing. But the level it's at remains intolerable and a real financial risk to individuals and businesses. I'm personally aware of several people who've been scammed of thousands of dollars within the past year.
Cut phone service and that threat disappears, along with all the attendant billing bullshit and customer service nightmares.
Is the industry aware of this and what if anything does it plan to do?