Correct me if I am wrong but doesnt Apple iPhone 7 also have wireless headphones. The USB type C port is an alternative method to connect.
So you can still listen on wireless headphones and charge the phone. Why would you need an adapter.
1. Because your wireless headphones are also out of juice and have to be changed.
2. Wireless headphones are an additional cost item and most people will use the lightning headphones which come bundled with the phone.