Why there are only imported oral contraceptives having no patent?

There are the total 11 oral contraceptives distributed in Korea.

Among them Crown Pharm’s ‘Sexcon Tab’ is the only product manufactured in the domestic industry; however, its market share is less than 2%.

Every famous products, such as Mercilon(Bayer, sold by Yuhan), Minulet(Pfizer, sold by Ildong) and Myvlar(Dong-A Pharm), are all imported drugs.

Also, recently-launched approved products of...