While things are still experimental, I think the current approach works best.I kind of mispoke in the OP, I meant where VR will eventually be heading. Not that VR should be standardized right now.
Long term VR headsets should either be like computer monitors or be complete solutions ala Oculus Quest. Short term however things are too volatile. Standard headsets are somewhat plug and play on PC with OpenVR but the second a headset/controller attempts something novel, a lack of standards is beneficial.
Take for example something funky like a wireless VR headset that applies reprojection within the headset itself to decrease latency. It'd specifically need games to render the game to two separate images so that reprojection isn't applied to HUD elements. As a peripheral, this new technique could be "forced" into existence the second it makes sense. If a next gen system wanted to do this they could just do this and that'd be that. If however VR worked like computer monitors/TVs, this new technique would be slow to implement ala G-Sync and take a while to gain serious support. By that time a better VR technique could be developed.
There's a lot of pros and cons with the way it's done right now.
Example:
-fragmentation
+easier for a better technique to become more dominant
On a related note, Oculus has been doing really great in that, there's a layer for their software so that games can take advantage of some of the new developments without the dev having to do any work. They added ASW that way for example.