A lot of disciplines are organized into strata, where once you are on a particular stratum in terms of what you know, you can get a lot done without learning new things. The truly new ideas tend to occur in corner cases or logical extremes, and generally people discount such things as being too focused on insignificant details. However, these corner cases often lead to new strata. I suspect corner cases define the history of ideas.

So, when working on practical problems, since they are the general case, it is hard to see the value of special, stratifying issues.