It's from an era when interoperability in a then-very-small universe was very important to moving the Internet forward. Back then there were no spammers, and v

It's from an era when interoperability in a then-very-small universe was very important to moving the Internet forward. Back then there were no spammers, and very few bad actors. It's possible that the "Postel law" helped for a while -- hard to say for sure though.