Wigs have been worn since well before Christ was born.
Most notoriously by the Egyptians (men & women) who shaved off their hair because of the heat and then wore wigs for formal occasions.
They exposed their hairlines, as have wearers right up to the present day.
The only thing that has changed is the success at creating a more natural appearing hairline.
More recently, actors on stage & screen have driven the development of hairpieces.
Since film & TV became popular, actors have worn pieces with exposed hairlines.
Wig making has had to keep up with the increasing clarity & definition of filming, until we have the products we know of today.
High Definition will push that even further.

I think you'd have to be more specific in your question to get a more specific answer.