I have a DisplayPort based monitor, and a laptop with a DP out. I recently got a second laptop with HDMI out, and went looking for a HDMI -> DP converter. I was very surprised to find that such a thing effectively doesn't seem to exist.
This answer and the Dell page it links to seem to imply that it's just not possible to go HDMI -> DP, without a very expensive converter box (not just an adaptor). However, I can't find anything that explains why this is the case. Is DP designed to be backwards compatible but can't interpret HDMI? Is it a case of HDMI-quality signal not being high enough quality to be convertible? Some other reason?
Note that this question is not looking for an adaptor - I'm looking for the underlying cause of the lack of them.