Rabbi Moshe Sternbuch said that:
aside from the actual prohibition of wearing such wigs, which cannot be distinguished from real hair, those who wear them are denigrating the holy Torah and demonstrating that they are embarrassed of Judaism, which requires them to cover their hair in a distinguishable manner. They are adopting the attitude of the maskilim, whose motto was: “Be a Jew at home, and a person outside”.
But permitting wigs as a hair-covering is the road to better and better wigs, just like any consumer product!
“Who is wise? One who foresees consequences.” ואידך זיל גמור
We wrote about this halfway-house nonsense earlier here…