»But in todays CPUs there is no advantage using the short thing. You can add 64 bits or 8 bits, takes the same amount of time. And you look up what is the cash value of having saved seven bytes on a number. When you add that up it is zero. So there is no benefit.« [1]

As long as you are concerned with adding a bit of eye candy and interactivity to a web page this may be true enough to get away with the JavaScript way of making every number a double precision floating point number but there a other domains where this will not fly. And even in the world of JavaScript asm.js is trying hard to overcome this limitation.

[1] http://www.youtube.com/watch?v=bo36MrBfTk4&t=42m17s