I have 5 sets of dice total. In our games I set up 3 of them on my end of the table and 2 of them on the other end of the table.
Over the evening they'll get passed around between people so they're not organized anymore, but mainly I just like being able to have them in order when we start.
That, and being able to count them easily to know I haven't lost any. It makes me happy to see them all lined up, but I don't have any superstitions about high or low-rolling dice.