Why do street map applications use a bar scale rather than a representative fraction or verbal scale?

Street map applications use a bar scale because it includes the amount of distortion the user can expect on the map.

Street map applications use a bar scale because the user can apply any units to it as long as the units are the same.

Street map applications use a bar scale because it defines the symbols and colors used throughout the map.

Street map applications use a bar scale because it remains accurate when the user changes the map's extent.