Because the demand for HiDPI desktop displays isn't there yet. You would buy one, and so would I, but overall they wouldn't sell much, compared to the standard 1080p panels. We have to wait another year until Apple introduces Retina iMacs, tells everybody how awesome they are and why people absolutely need Retina displays.
Then suddenly there will be steep increase in the demand of HiDPI panels, and a few month later every manufaturer starts offering them. If I learned anything the last few years, it's that's how it works.
So, we all agree that "Retina" displays are better? The problem is that it won't become popular until a company, which tends to be Apple, comes along with the right marketing so the average consumer feels the need to spend the extra money on the technology. Personally, I wouldn't mind if Microsoft joined in and promoted HiDPI, for example, with Windows 8.
Apple introduced USB in the later 90's. It took forever before the PC industry adopted it. I don't think anyone has to pay licensing fees for Thunderbolt connectors. How long do we have to wait before every PC ships with a port?
