Let me explain..
Hair transplants are performed by taking hair from one part of the scalp and surgically placing it into areas of baldness. In order for a hair transplant to be successful, the harvested hair must come from a DHT resistant area, typically the back of the head. For most men with male pattern baldness, the sides and lower portions of the scalp are not affected by DHT, so this hair may be used to repopulate bald areas. Men, and women, who suffer from diffuse hair loss, or hair loss distributed across the entire scalp, may not benefit from hair transplants, as DHT sensitivity likely affects the whole scalp.
Hope this helps