The red is what is missing from 1920x1080 compared to 1920x1200:
I look it at it quite simple according to aspect ratios:
Monitors: 4:3, 5:4, 16:10 (8:5)
TVs: 4:3, 16:9
The reason why the monitors are a little bit taller is for the menus. You can have a 1080p film displaying and still have some workspace.
Physical dimensions of a screen also doesn't limit resolution, the DPI does. For example, my monitor Samsung T240 (20.375" x 12.75"):
pixels per inch = pixels / width
x: 94.23 pixels per inch = 1920 / 20.375"
y: 94.12 pixels per inch = 1200 / 12.75"
There's monitors out there that are close to double that figure. Even though they are only 23/24" monitors, they feature resolutions of 3840x2160. Small screens with large resolutions have better picture clarity than large screens with small resolutions (e.g. a 24" with 1920x1200 has higher DPI and therefore clarity than a 24" with 1920x1080 resolution).