Imagine thinking that dropping expats and international travelers is a good move though.
Not everyone has a smartphone, but that's not what is required. Just a mobile phone that can receive an SMS - and phones have been doing that for 25 years or something.
There's nothing trustworthy about the people who issued me this current sim card. There's no reason to assume I would want to link it to any account, even if it was allowed. Even if I were inclined to trust this process and if it were possible, I'd have to be using this provider when I am in a 3rd country or in my "home" country.
It is just a nonsensical set of assumptions on PayPal's part.