Neoprene gaiters are an essential part of the boot. They improve the boot fit and prevent rubbing. If you ride in wet conditions a lot, or use the boots 24/7, a spare set of gaiters is handy, so you can swap to clean, dry ones daily.
If necessary, you can buy smaller or larger neoprene gaiters to improve the boot fit even further. And the gaiters are available in lots of fun colors, so you can pick your favorite one!