Why doesn't Apple use the logo at the back of the iPhone as a fingerprint scanner?

Why doesn't Apple use the logo at the back of the iPhone as a fingerprint scanner? - 1

It's not protective cover friendly.

I use an android phone whose fingerprint sensor is indeed on the back of the phone, and using protective cover often obstructs access to the small area of the sensor, I have stopped using it for this reason.

Home key would most likely be my preferred location, since that part is usually never cover protected.

Unconventional

They aren't that smart.