Why don't they make more advanced DX lenses?

I know DX sensors are considered "beginner" or "amateur" cameras because they generally have lower quality than FX sensors. But as technology improves and DX sensors get better quality, I wonder if they could become the new standard for practicality reasons. Lenses for DX can be more compact due to the smaller sensor size, so why do they only make beginner lenses DX only? They could probably make a comparatively compact 70-300 VR if it was DX instead of FX, and it would probably be cheaper too. It seems there's always a premium for FX. Or for the size of the actual Nikon 70-300 VR FX maybe they could make a 70-400 VR DX. Speculating of course.

Anyway, I'm just an amateur so perhaps I'm wrong, but anyway, what are your opinions on the matter?

Added (1). @lucienhu - My point is that you can make DX lenses smaller and cheaper. For me to get, say, a 70-200 F2.8 is impractical in price and also it's not a lens you can just carry around, it's very big and bulky. If they made a similar lens designed for DX only, perhaps it could be a little more practical. And same with the 24-70 2.8, which while still useable, is still rather big and is obviously very expensive.

Couldn't you just get a shorter FX lense? I can't see much point in pro DX lenses when you can just get an FX lense that will fit any body.

I would be annoyed if I had bought pro lenses for my D7000, and say if I wanted to upgrade to the D4 I wouldn't be able to use my lenses.

I see your point but I can't see any reason for NIkon to do this.

One of my best lenses is the 17-55 f/2.8 DX. Not cheap. Otherwise, they probably feel that there just isn't a large enough market to really develop a DX line. They have recently started bringing out some DX primes, so maybe…

You make a valid point, though

You might be interested in this: http://www.popphoto.com/gear/2012/09/tamron-working-70-200mm-f28-di-vc-usd-telephoto-zoom-lens?src=facebook

DX is simply for crop sensors. Large apertures are associated with larger optics. Blame that to physics. It wouldn't make sense to limit a large piece of glass to project an image to a smaller than usual rectangle hence the FX designation. There are some large aperture DX lenses and they are stretching the limits to reach it. If you just feel sorry you can't afford the expensive lenses, turnaround completely and buy full manual single-focal length film lenses. They are relatively cheaper and can put many digital lenses to shame.