When technology changes, so should we.
When I started doing website development, not that long ago, the standard screen resolution was 800x600 and some people had the new 960x720 screens. The standard at that time was to design for a fluid screen width with the difference between the smaller screens and the larger screens being relatively minor.
The site w3schools.com shows that in the year 2000 their average visitor had a screen size of 800x600 with only 4% with a screen size larger than 1024x768, whereas in January 2013, 90% of their average visitor had a screen size larger than 1024x768.