The fruit trees in my backyard have quite a bit of grapefruit in the upper branches. This leftover fruit requires quite a bit of extra effort including scrounging up a fruit picker that still works. More importantly, I actually have to think about picking the tops of the trees. Interestingly, exactly the same thing happens with genealogical research.
Finding your entire family in the U.S. Census on the first try, is like low hanging fruit. It takes some effort but not nearly the effort that more obscure records and sources require. Fair weather genealogists are satisfied with low hanging fruit. But when the going gets tough, the tough get going. On the other hand, why ignore the low hanging fruit? If its there, grab it and use it.