People should really learn to set up their UI properly. UI Scale isn't needed at all if you set the size of frames properly. Since small things don't need to get scaled down even more, right? A lot of default addon's frame sizes (height, width) are just way to big for the normal user, but then again changing the size is a solution that doesn't need an UIScale, too.
It does help to get things to be "pixelperfect", though.
Because of the way WoW handles texture sizes depending on screen resolution. It's not the only way, however. It helps to avoid size values and frame positions that are uneven (121, 13, ...).
