Semago -
I think it comes down to 3 major factors -
1) Clear water. Many of our waters are much clearer than those in the mid-west/South. In many of the lakes I fish the visibility can often exceed 10 feet. The bass get a really good look at the lure so we see alot fewer "reaction bites".

2) Fishing pressure. In many of our natural lakes there are relatively few bass. It is not uncommon for there to be only 1 or 2 bass over 12 inches long per acre. In addition these fish are much slower growing than in waters to the South. In Washington the average might 5 years for a largemouth bass to reach 12 inches. Doesn't take much pressure on a population of fish that is both old and has a low abundance to "wise-up" the fish. 25 years ago a white spinner-bait was a near universal bait - you could catch a respectable bag with one on nearly any water in the state.

3) Different food sources. On many of the waters to the south and midwest shad are a major food source. Also because of the slow growth of the bass fish such as the sunfish aren't really available to the bass to any large degree. As a result the major food sources are such things as crawfish, sculpins, and salmonids.

Just my thoughts
Tight lines
Curt