for us it was dr's recommendation, but we still wanted to try one more time. He first suggested it after first round of injects, but we said we wanted to try one more time. He said he understood that and respected our wishes.
We did that and it didn't work, so we said we were ready to switch to IVF now. He again told us that we understood we wanted to try that one more time with IUI and that we had to do it at a pace that we were comfortable with and would not regret later.
(our DX is PCOS/Endo. Endo was removed and I respond to meds well, so dr is not sure why we havent' gotten our BFP, so in a way we are unexplained IF)