Desktops: Software is so far behind due to the long shelf-life of PS360 consoles that if you have a Core i7 920/860 @ 3.9-4.0ghz, unless you have GTX780 SLI or faster, the performance increase in games will be marginal by moving to i7 4770K overclocked. Even a stock 1st generation i5/i7 is more than sufficient for office work, e-mails, facebook, youtube, etc. Those consumers are not going to go out and buy a new PC for this basic work. For the rest of us PC gamers, we don't buy pre-assembled systems.
Next, laptops. People are starting to realize that it's better to spend a little more and get a light laptop, with high build quality, awesome screen, good trackpad, SSD, strong battery life and one that manages to have a good resale value after 2-3 years --> Apple. While PC shipments declined last quarter, Apple managed to ship 28.5% more units in the US.
http://www.techpowerup.com/196707/gartner-says-pc-shipments-down-6-9-percent-in-q4-2013.html
How is that possible? Their products are more appealing as people are getting tired of buying cheap $500-600 laptops that become slow in 5 months.
Then there are younger and older generations. My parents have a 6 year old laptop and instead of getting a new laptop, they went out and bought the latest iPad. It's perfect for them when they travel, or perform basic things at home. My dad uses a workstation at work, which means he doesn't need a powerful laptop at home. Younger kids run around and for them a lighter device is far preferable. Again, tablet wins over laptops for them. I've seen many girls carry from the ages of 16-23 carry tablets in their bags with them. It's a lot harder to fit a laptop in there....
Also, if one already has a modern laptop with an Ivy Bridge CPU, 8-12GB of RAM, 1080P screen, drop an SSD in there and you don't need to buy a new system for 3-4 years. PCs are now very fast for basic work that unless you are rendering, video encoding or running games, laptops last longer than ever.