From Best Buy (BB here on) for Xbox 360:
"More connections
Plug into the possibilities using five USB ports, an Ethernet port, an HDMI output and an all-new integrated optical audio out port for an easier connection to the booming sound of your A/V receive"
No DisplayPort.
From BB for Playstation3:
"HDMI output for 1080p resolution. Ensures that visuals come alive with incredible depth and clarity on your high-definition screen."
No DisplayPort.
Are X360 and PS3 computers? No. Your point is irrelevant. As said above, HDMI is meant for TVs and DisplayPort is meant for computers.
Cameras, cell phones, TVs, audio/video receivers. All the electronic gear that people use.
All of it that is not made by Apple.
You forgot that those are not computers. HDMI as the only video output would be a huge downgrade. What exactly is your problem with MiniDP? All you need is a simple adapter and tadaa, you have HDMI port