I would guess that most of my grandchildren refuse to eat the crusts of slices of bread and the heels of the loaves are often not eaten or even thrown away. I see this a failure to come to grip with the reality of life, that is, life is mostly in the crust. Almost anything worth doing is difficult. But even when we have mostly overcome our childish propensity to leave the difficult tasks and only do the easy ones, we have to fight that tendency all of the time.
For example, we would like to believe that all that we need to know about our ancestors can be learned from the U.S. Census records, that is, the white air bread centers of our genealogical loaves. This reminds of the reaction of some of my grandchildren to some "12 grain bread" we had for dinner. There was quite a controversy over what each of the ingredients might be and whether or not the ingredients were "acceptible" for consumption. In the end, they refused to eat any of it.
When do we know we are "eating the crust" so to speak? I believe it is when we begin extending ourselves into new areas we have never researched before; such as learning German Black Letter Script or studying out 16th Century parish registers. In the U.S. it may be learning about probate or beginning to understand land records. In every case, moving into a new area of research is like eating the crusts of our research loaves. One thing I can say is that after a while, you will begin with the crust and relish it for its consistency and nourishment. You may even go on to eat 12 grain bread!