Well, Avid must see some benefit

Square and Non-Square Pixel Modes

External NTSC monitors, like you would use to preview your work in Final Cut Pro and Avid Express, display video quite differently than does your computer monitor. Standard definition equipment, such as a television set, uses non-square pixels to display an image while your computer monitor uses square pixels, therefore making the image you are preparing within your NLE for broadcast appear distorted.

Found this after some searching, ah the bittmann would be proud of me.

To dig deeper into this topic of "Square vs. Non-Square Pixels."

Here is a little from that link

But, first, some background. The smallest element of a picture is the pixel (short for "PICture ELement"). On your computer screen, all pixels are square. However, on a TV, pixels are rectangles. This means that if you are creating graphics on your computer to display as part of a video program, you need to compensate for the differences in shape between the two pixel sizes.

If you don't compensate for these differences, the circles you create on your computer will display as long, thin ovals on your TV set.

And just one more source, Adobe has some info here