Image by Wikipedia user Citynoise using NOAA data.
If you look at this map of tropical cyclone tracks, you'll notice that there's a gap in the central northern Pacific where tropical cyclones generally don't go. On the edge of that gap, you'll find the Hawaiian Islands. Further, although the islands are sort of in the fringes of the eastern tropical cyclone area, they're in a gap in that fringe -- tropical cyclones forming in the eastern Pacific track either north or south of them.
So, why don't tropical cyclones hit Hawaii?