Yes that is curious. Apart from the Nikon 10.5 fisheye, and the Canon 24 STM, I can't think of any compact wide "DX" DSLR primes from the two main players, or any third party manufacturer. Plenty of wide zooms, including some fast limited range zooms by Sigma and Tokina, but no primes. Yet that is what people have been asking for, for years. You'd think there would be a ready market and at least one of the third party makers would have stepped in by now.
There will be a good reason. Tokina, eg, previously made a 17mm f/3.5 FX and they make DX wide zooms, so they have the know-how to make a wide DX prime. The obvious reason they don't do it is they don't think it will make money.
Because DX and FX have the same registration distance a (say) 15mm for DX has to be as retrofocus as an FX 15mm, which creates the same degree of asymmetry and therefore distortion and coma for both formats, and the same need for correcting elements - or, as in the case of the new 10-20, small maximum apertures. The DX lenses need less covering power, so the front element does not need to be as large as for an FX lens of the same actual focal length, but there is little or no DX benefit at equivalent focal lengths for wide lenses: the Nikon DX 12-24/4 is exactly the same price ($1000) and size (77mm filters) as the 16-35/4 FX, and the 10-24 DX variable aperture is the same size as and more expensive than the 18-35 variable aperture FX.
DX wide primes would have to compete not only with the DX wide zooms, but also with the option of going FX. Most FX lenses in the 14-15mm range are buttock-clenchingly expensive, and it is not obvious that 14 or 15mm DX primes would be price competitive with either alternative. The 14-24/2.8 FX is, in round numbers, twice the price of the 12-24/4 DX - it is also a stop faster, but if we take that price difference as the DX benefit at the same actual focal length a DX version of the Nikon 14/2.8 might cost $900, and a DX version of the Zeiss 15/2.8 might cost $1000. That is not competitive with a zoom for a casual user, and for a serious wide-angle user it is hard to see it as competitive with buying an FX body and a 20/1.8. (The Irix lenses may break the mould, if it turns out that the cost is low only because they have reduced their profit margin).
Many people - including me - say they want wide DX primes, but when Thom Hogan asked his readers to rank possible lenses according to how likely they would be to buy them the picture changed: zooms were the first choice (
http://www.dslrbodies.com/newsviews/desirable-dx-lenses-accordi.html).
