Even were this not the case—short of an arrest, there is no way for the federal government to “serve you” in a contactable manner—whereas my sense is that this is not the case in Estonia and a growing number of spam nations, ie the government can mandate that citizens be reachable digitally (e.g. portal login is sufficient). The IRS has no inexpensive and scalable way of proving that the person on my end of the Internet is the person with the SSN in the filling (login.gov is great but not pushed throughout all the service branches).

I have to disagree here. It's not about the middleman. They probably know the income you made -- but they may also not know all the income you made. Self reporting of taxes is standard in many countries for this reason. People run small businesses, freelance, get cash payments, tips, etc that are outside their normal (reported) income. You are required to report this, even if the IRS doesn't know about it. That's why they will never send you pre-filled forms. They want you to report everything -- and they're certainly not going to make easier to skip reporting some of your income.