Personally, I believe that part of the problem is that PCs are no longer a new and exciting thing; correct me if I am mistaken but the overall growth of the market is actually.... negative. I believe only Apple is selling slightly more desktops than the industry average (growth in %, obviously). Otherwise, it's a mature industry now, and companies will try to maintain this for as long as possible. Focus on new things, like smartphones or the connected home and even cars, will be new innovations.
if anyone would like to mention something great that can be added to desktops other than faster processors, memory and/or storage. I think the industry would be more than willing to listen. I imagine whatever you want would probably be subjective, like I don't think having a DVD drive is a good example at all. Eventually, we will probably see much smaller, more powerful and connected computers in the future, but society will have to catch up. Maybe we'll all be walking around with smartwatches that can monitor our bodies, homes and online presence all by itself.