Also, ironically, the only spam I get these days is via text or robocalls.
I'd gladly get rid of my phone number altogether, if it wasn't for businesses insisting on using it as a primary user identifier, verification method, and communications channel.
At least we both agree on how we would get rid of our phone numbers. But the reason businesses use it as a verification method is because it is hard to get one - and it costs $$$. It’s basically a outsourced, ubiquitous, federated human identity service.
Notice how they all filter out voip numbers - because voip numbers are too cheap to acquire to rely on as a filter. They assume that only humans would pay the monthly charge for a landline or mobile number. So $$$ to pay for phone service is used as the universal “captcha” of last resort.