Having researched and published in this area of Pain Medicine over the last 25 years, I can say with complete confidence that there is no rational sceintifc reason for therapists (or medical practitioners) to practice "dry needling". The existence of trigger points as primary sources of pain has never been confirmed and the relevant literature fails to reveal benefit to patients over and above that of placebo therapy. 

In support of my position, I attach this list of references:

Quintner JL, Cohen ML. Referred pain of peripheral neural origin: an alternative to the "Myofascial Pain" construct. Clin J Pain  1994; 10: 243-251.

Cohen ML, Quintner JL. The horse is dead: let myofascial pain syndrome rest in peace [letter]. Pain Medicine 2008; 9: 464-465.

Quintner J, Bove G, Cohen M. A critical evaluation of the “trigger point” phenomenon. Rheumatology 2015; 54: 392-399.

Quintner JL, Cohen ML. Myofascial pain: a bogus construct. In: Hutson M, Ward A, eds. Oxford Textbook of Musculoskeletal Medicine, 2nd ed. 2015.

Quintner J, Bove G, Cohen M [letter to the Editor (matters arising)]. Comment on: A critical evaluation of the trigger point phenomenon: reply. Rheumatology 2015: doi:10.1093rheumatology/kev095.

Quintner JL, Bove GM, Cohen ML. Response to Dommerholt and Gerwin: Did we miss the point? J Bodyw Mov Ther 2015; 19: 394-395.