Consumer DNA testing has basically seen to that.
"The concept of anonymity has been hammered into the model of sperm donation since its inception. The first recorded instance of artificial insemination with donor sperm occurred in 1884; the woman was never even told that another man’s semen was used. The fear, apparently, was psychological — it was believed this might cause “irreparable harm” to the marriage and to the child.
Infertility carried a stigma for many years, and still does today, particularly among men — even though they contribute to about half of the infertility cases in the world. As a result, sperm donation was shrouded in secrecy, even looked upon with shame, for nearly a century."