Most displays get advertised with either 16:9 or 4:3 display ratio. However, if you compare the resolution with the display ratio, it's most often neither of both.
For example, the resolution of my notebook display is 1366x768.
But 1366/768 = 683/384 != 688/387 = 16/9
Another common resolution is 1920/1200 = 8/5
But for some resolutions it's correct:
1024/768 = 4/3
800/600 = 4/3
Is there a technical reason / user experience reason for this? Why do displays have other ratios than what they get advertised?
(I assume that every pixel is a perfect squre. Is this assumption wrong?)