It baffles me what the secrecy is for.
That's an aspect of it, yes, but fundamentally it's a "simple" feature that the system should be able to provide with far less drama than it has.
People have been creating "email" systems for 50 years, and there's no reason this one should be so finicky (obviously there is a reason as to why it's failing, but there's no excuse for it).
While it may only take a little bit of research to hunt down someones contact information, bots turn out to do that very poorly.
I just marvel at my phone answering machine. Some machine somewhere is out there blindly calling soulless, empty, stupid other machines.
"Have your bot call my bot and they'll have lunch."
It's a complete waste of everything. Power, time, life, everything. But, they're fishing. 1 out of 10,000 they might catch someone. So, we all suffer.
So, it's not so much trying to prevent folks from knocking on our doors, it's about just lowering the din of waste going on that's systemic in modern communication.