I guess you live in US. In my country (Turkiye) every commercial SMS sender needs your permission to send advertising SMS. This usually happens when you sign up for a website/app, an optional checkbox to allow commercial communication via SMS and email. There's a second (mandatory) checkbox for an agreement regarding our version of GDPR.
Every advertising SMS includes a shortened link or something like "text DENY to 1234" to be able to opt-out of them at any time. To date I've seen only one vendor which still sent SMSs after I opted out, which I promptly sent a complaint about to our presidency. No more texts after that. Every email is the same, with an unsubscribe link. I've encountered only one brand which didn't comply and I blocked them in the Mail app.
Even when it is this simple to block spam most people I know still don't do it. They are in a rush, stressed, commuting, with kids running around, doing something else simultaneously. Too busy with life, checking all the boxes in a hurry, scrolling past all the advertising spam to find the one message/mail from their contact. For many, it needs to be literally zero effort, fully automatic.
There are those SMS scams from foreign numbers which go like "Thanks for signing up for our job offer, please send your card details to get the $1000/day payment". But they are rare, once a fortnight at most IME.
We don't get physical advertising mail. Maybe cultural? Not economical? No one bothers.
Everyone gets calls from a fiber high speed internet company every once in a while. Since people are able to recognize the recorded voice so fast and close the call, now they added a several seconds delay before playing it. I don't know what makes fiber internet vendors special, since I only ever get those calls. Telecom-ISPs intentionally not blocking them?
And those WhatsApp calls from third world numbers. Once a month maybe, but this is Meta's problem.