This is a really really old page. Interesting for historical reasons, but the limit isn't really there any more.

I agree the limit shouldn't be there, but the majority of web servers in common use don't use these techniques and so still top out at a few hundred connections, for whatever reason...

Sure. It's not a hard problem any more, but as you say, a lot of web servers still haven't had the pressure/motivation to fix it yet. Presumably some of that is due to so much being built on top of apache etc, they have come to rely on 1 thread/process per connection, so it's hard to change from that.

It doesn't seem to mention yaws, the Erlang web server.

http://www.sics.se/~joe/apachevsyaws.html

The C10K page is historical; it's about 5 years old. Now that the Web serving problem has been solved there's not much point in updating the page.

Why was it posted, then?

This page is talking about implementation techniques for webservers and other network servers, not comparing webserver implementations themselves.

It does list webserver implementations at the bottom.