l-glutathione vs glutathione which is better vs. Other Antioxidants: What Sets It Apart? – Setu Nutrition L-Glutathione Reduced - Super Antioxidant

Science 345 , 295298 (2014)

In a controlled study with women showing signs of photoaging, a GHK-Cu facial cream used daily for 12 weeks led to visible reduction in wrinkle depth and fine lines, outperforming both placebo and even a vitamin K cream

Seiwerth, Sven

Barometer respondents find that patients most commonly access peptides through med spas (55%), online retailers selling products labeled for research (45%) or compounding pharmacies (43%) (note: respondents could choose more than one answer.) This leaves physicians sometimes needing to step up to manage downstream issues from medications they didnt prescribe

Combine that with three other properties it's sterile, it's pH-neutral and gentle on most peptides, and it's inexpensive and it becomes the obvious default diluent across the field