This isn't the case with mobile numbers everywhere in the world. Spam calls here are pretty much nonexistent. It doesn't have to be this way with E-Mail either - we just need to prosecute spammers (including marketers) and make new laws where needed. Then you can accept almost all mail from cooperating countries and only need to block mail from countries that do not care about preventing spam.
Enormous amounts of email will be generated but no one will ever see it.