I think it's a fashion that always existed. What about Kelly? Shirley? Tracey? Lindsay?
Kelly was already pretty common in the 50s and 60s. Same with Tracey. Shirley was super common in the 30s, I think. It's not a very recent trend. In 1849 Charlotte Bronte named a girl in one of her novels Shirley. I think the father of the character Shirley had intended to give the name to a son and used it anyway when he had a daughter. I actually consider that a good thing. I mean women have surnames too, why can only boys have them as first names? What if some women would really like to give their maiden names to their daughters? I think this is how it all started anyway. I mean why are surnames considered masculine? Women have surnames too.