Duncan Black makes a really good point.
It wasn't so much the technology, though it was that too, it was the idea, and it isn't an idea a for-profit company would have pursued in nearly the same way.
I'm (just barely) old enough to remember all this. I started seriously programming computers in 1981, I had my first email address in 1983, and I can remember when my 1985-vintage email address was spelled
Thirty years, sadly, seems just long enough to forget all that important history. Thankfully, people like Tim Lee are around to help us remember.