It boils down to bandwidth. There's a fuckton of telemetry coming down from the spacecraft. You should see some hi res stuff in a few days.
Actually, it's probably a combination of factors. No doubt, the telemetry package for Orion has to be massive. Especially since NASA stated that they have as many as 1000 separate instrumentation readouts to relay.
But I work with technology on a daily basis that can compress a 1080i HD video signal down to 6 MHz for transmission via Ku or C band satellite uplink. Hell, with the right encoding I can even stream live HD video by bundling together streaming data from 3 or 4 smartphones. And considering the size of the antennae at the NASA tracking stations, they should have been more than capable of bringing in that signal even when the spacecraft was at it's apogee.
Bandwidth probably wasn't so much the issue. More likely, it's one of the classic challenges of spaceflight: weight. The weight of the gear that would be needed for that type of HD video encoding was probably the deciding factor for NASA. HD cameras, like GoPros, are really light. But the transmission gear? That's another story. NASA has been using Standard Def video transmission gear on manned spaceflight for years and probably has some very light gear at their disposal. As for cameras? NASA very well may have had something like a GoPro onboard Orion. I'd definitely like to see that footage.