Personally I find about 95% of my use of field guides is at home, either before or after birding. Only rarely do I actually carry it afield with me. Is that markedly different from how others utilize them?
Here's one birder who won't go into the field without a field guide relevant to the location. A testament to my shortcomings no doubt, but I've encountered many others with a similar dependence.
Hence my concurrence with the sentiment that Hawaii birds be treated separately.