The only reason is that you happen to speak English. If you grew up speaking some of the other languages that are popular around our globe, you'd call it something else. Here are a few examples....
Because. That is how the English language has worked for years and years and years and makes the most sense.
Looks like its this song one by three dog night http://www.threedognight.com/l_one.html
It's when you put you are code and the rest ones, like this (AREA)-111-111
lets call the number we are looking for Y. Y x 2 / 3=14Y=(14 x 3 / 2)Y=21one third of 21 doubled gives you 14.