I don't see that many people (men) even drinking beer on domestic flights so I'm not sure there would be a huge demand for the hard stuff even if it was available. Actually, I am very relieved that Chinese domestic flights remain hard-liquor free. IME Chinese don't hold their liquor well, and I shudder to think...
I don't find this a hardship though I am not much of a drinker and especially not on airplanes whether short or long haul. Chinese flights for me are usually pleasantly uneventful and I'd like to keep them that way. Now USA domestic flights is another story--generally after I disembark, that's when I feel the need for a stiff drink to help recuperate.