I very frequently use netcat (or openssl s_client for HTTPS servers) to connect directly to a server I am debugging.

It could be argued that there is no "need" for this, but I find myself doing it quite frequently all the same. That may have something to do with the fact that I am developing a relatively low-level reverse HTTP proxy tool (PageKite), but I also did it quite a bit when working on more traditional webapps.

Once you speak the protocol it's nice to be able to just connect and chat with the server directly. :-) Humans are really bad at speaking binary.

I don't know. Probably not, but it's sometimes convenient to do so.

Well, I've did so when I had to debug some redirect caching problem with "walled garden" setup. This could also be done with a more specialized software, though, I just happened to use telnet as it was readily available.

I also sometimes check server's availability (and overall response correctnes) by telnetting to it. Although, I was just too lazy to set up a tunnel to the LAN they're residing at.

Whilst you can use more dedicated tools for debugging http connections than telnet, there is still an argument for protocols simple enough that you can use telnet.

Take Arduino for example, writing a naive but working http client is childs play; writing a SPDY client in Arduino is well beyond many people's capabilities. Yes libraries will appear eventually, but we've not even got a decent open http library yet.

I most commonly do it to read the HTTP headers using HEAD.