Way back when wigs started becoming acceptable I don’t think they looked like hair at all ;)Did you ever see a synthetic sheital?? 🙂
I’m just speculating here and could totally be wrong (probably am) but many women in the olden days didn’t cover their hair, the Rabbanim could’ve thought that it’s better that the women cover their hair even with other hair than not cover it at all. I’m just guessing.
Also, I don’t know a lot of non-Jewish women that cover their hair. If you think about it this way, all other religions that forbid womens hair to be uncovered cover it with cloth. So maybe wearing a tichel or other cloth covering is considered chukas hagoyim. 😉