Lots of dumb phones are trojaned on a firmware level. Trojans are different, but in general they allow the third-party (malware author) to accept SMS and forward them over internet. This is used to register accounts on a services which requires a phone number.

Here's my article about that from 2021. It's for the devices sold in Russia, but this issue is worldwide: https://habr.com/ru/articles/575626/

And here's more detailed research of two particular devices: https://notes.valdikss.org.ru/trojan-digma/

"Can we freaking sell them dumbphones"

Nothing is stopping the guy at Walmart or Tmobile from selling them dumbphones, or are you implying they are forced to?

Try letting the blame trickle down from the pyramid's apex instead of blaming the footman.

Here is the first iPhone ad:

https://www.youtube.com/watch?v=6Bvfs4ai5XU

The ad depicts it as a mere phone instead of a potentially hostile Turing machine. There is equivalent messaging in the android ecosystem but its advertising is not so ubiquitous.