Comment by badc0ffee

Displaying content from a DVD on a panel with square pixels (LCD, plasma, etc.) required stretching or omitting some pixels. For widescreen content you'd need to stretch that 720x480 to 848x480, and for 4:3 content you'd need to stretch it to 720x540, or shrink it to 640x480, depending on the resolution of the panel.

CRTs of course had no fixed horizontal resolution.

Edit: I just realized I forgot about PAL DVDs which were 720x576. But the same principle applies.