It is not "all or nothing".

it's defense in depth, and if masks, which are literally dirt cheap and only a minor inconvenience are even somewhat effective, that adds to the overall mitigation efforts and should be mandated.

It's not hard folks.

"Turning off SMTP relay only prevents other people from getting spam. I'm not going to do that, even though it's a one line configuration change and doesn't really impact my use case. Moreover, the default should be open SMTP relay"