Why are lattes often served in big, wide cups? Lattes are often served in a cup that looks like this:



Apart from size, is there a particular reason for the shape of the cup? I know that, with cocktails, the many different cocktail glasses you can get are suited to different kinds of drinks. I'm assuming it's the same here, so what is it about a latte that makes it suited for this shape of mug?
It may be just me, but I think it has to do with aiming for a ratio of foam to liquid in each sip.

Basically a taller cylindrical cup with the same amount of foam on it would cause the first couple of sips to be mostly, if not entirely, foam. With a shorter wider cup you can have a lot of foam, but in a thinner layer, allowing for a more balanced sip and better mouth feel through the duration of the cup.