Or maybe it's an overly competitive protocol? Like playing Monopoly. Even a neophyte can end sweeping the game despite not understanding any of the underlying mechanics that drive the game's outcome. Those remaining mail providers are also fighting back the insanity. They 'just' won.
Don't hate the player, hate the game.
You can't put these big tech monopolists into the same bucket as normal companies. They have way too much power, and even when they do not intend to smash things, they end up smashing things.
SMTP is text based and we’ll defined, so I would also argue that the transport being “simpler” is nonsense.
Nothing is easy about email! Having worked for years just to get reliable in and outboxes is definitely not trivial. Also SMTP is a system out of your control if you want anything verified and actually delivered.
Say you enter a form at a company,and in the message box you just leave that code so they can mail you.
And in practice some minimal address obfuscation has been enough to block any address harvesters, and setting up a contact form or something comparable (and I guess especially also subsequently keeping it spam-free!) would have been much more of a hassle.