Outsourcing your weaknesses makes sense in the abstract as a comparative advantage play; but think of Coase as a counter. Why are there corporations at all, and not exclusively one-off networks of specialists? The most popular answer is transaction costs, and I think something comparable has bearing on this question.

Continuing the earlier example, it may be trivial to solve my math deficiencies by market-contracting whatever the math need is, but that's assuming I'm capable of knowing what needs to be contracted or understanding its proper scope. If I'm an F at math, the prospect of being able to make the requisite contract becomes tenuous.