The important question here is “Why vs.?” Why not see the fieldworker’s eye-witness account and what can already be found in libraries as complementary sources of information?

To me, Clifford Geertz’s account in the introduction to _Islam Observed_ nails the critical issue. We go into the field in search of insights that only first-hand experience produces–but their value can only be assessed in conversation with scholars pursuing other approaches. That conversation starts in the library (or, nowadays, on line).