It is a fashion thing. I like a bigger watch but not a giant one and this is because I have bigger wrists.
For size I draw the line at something like a rolex sea dweller. Can't remember the diameter but is bigger than my sub.
I guess I could see the need for a watch that big if your eyesight was fading...
The same as my view on ridiculously large women....don't be seen with them
Geez! Doesn't Flava Flav wear one that size around his neck?