Why is the VR implementation so poor?

I get your points, if I get a better graphics card the graphics would be better, but I do feel there are things the developers could do to improve performance. I can play on PC display on ultra with good frame rate, but with VR on lowest graphics settings I might get <5fps. Its just two stereo screens so shouldn’t be that demanding, but as others have said it could be the windows mixed reality adding complexity. I could get a new graphics card but it feels like I shouldn’t need to spend more money because its not been implemented well!