From Michael Atiyah’s essay Trends in Pure Mathematics.

In any given field of mathematics there are always some very fine points which present great technical challenges to the specialist but not are usually of interest to the general mathematician. To make an analogy, if you want to buy some hand-made pottery you are usually not interested in whether the potter used two hands or only one, though the potter would no doubt take great pride in his single-handed effort. In general the mathematical results that have the widest impact are not technically the most difficult.

This essay appears in the first volume of Atiyah’s collected works.

See his comments on this passage in this recent interview.