Aloha Ironraven,
Rain pants give you a pair of pants to wear while your regular pants are drying out, if need be. I don't know about you, but I would look pretty funny wearing gaiters with no pants.
Sorry for the visual. Happy New Year!
Actually, I don't carry rain pants or gaiters, just a pair of swim shorts in my pack plus the spare dry socks and underwear in a ziplock. And sometimes, I will lug a pair of sandals too if I expect to do a lot of stream crossings or think it will be really wet.
In Hawaii, there are a lot of pools to cool off in and you are really never too far from the ocean. Plus when it is really wet and mucky out, I really don't mind getting my legs wet too much, unless it is really cold. And it doesn't usually get really cold unless it is in the evening or early morning. I would usually be bundled up comfortably in a camp of some sort at those times.