Mostly, I think of pithy quotes as the conversational equivalent of icons in GUIs. If you don't already have a pretty good clue what an icon does, the icon by itself isn't very helpful... but once you become familiar with it, it can be very helpful.

Similarly, the nice thing about pithy quotes is that once you've understood the associated thought, they provide an easier way to bring that thought to mind on demand.

They can also provide a hook. That is, tossing a pithy quote into a conversation and providing additional explanation if there seems to be interest in it can be more comfortable than trying to toss a large chunk of exposition into conversation. (Well, for me, anyway. Some people seem more comfortable with tossing large chunks of exposition into conversations.)

All of which is to say, I'm fond of them.