Why is there no Media Center client?

Maybe I’m missing it, but Ive looked around for a thin client for Windows XP Media Center Edition, and I can’t find one, nor even find anyone looking for one. 

Media Center supports this idea of Media Center Extenders, that you can hook up to a TV use the Media Center PC from that TV.

MCE supports this through extensions to the Remote Desktop Protocol – on port 3390.  Try connecting to port 3390 using the standard MSTSC terminal services client, and it’ll bring up the login screen, but then disconnect you once you authenticate. 

The original XBox can be used as a Media Center Extender, and so can the XBox 360.  This works great – I use the XBox 360 to watch TV most of the time now – but sometimes I wish I could connect to the Media Center from my PC, and I can’t.

You can also get dedicated MCX boxes, that apparently run an embedded Windows and some software that works as a Media Center client.

Why isn’t there a software-based Media Center Extender?