Larger slices taste better, too. Kimchi starts to lose its crispness as soon as it is cut. If you store pre-cut kimchi in the fridge, it will turn into a floppy mess much sooner.
So you're more likely to be served uncut kimchi in restaurants where the menu requires fresh crisp kimchi, as in bossam, kalguksu, and seolleongtang.
Nice to learn that bit about long kimchi slices. I just assumed it was because people like it long, like with spaghetti.