For me, the most common scenario in which I'd want TouchID is when I have my phone resting flat on my desk. Depending on which phone case you may or may not have on your phone, the power button might be conveniently accessible. I'd prefer a version that didn't require me to lift my phone up off the desk in order to unlock it.
I have used phones with all types of fingerprint sensor. Below the screen (Moto Z, iPhone 6S), at the back, in the power button (Moto Z3), and built into screen (Moto Z4).
Built into the screen is by far superior of all. The worst is at the back, with power button at the side not far from it.
I think having it in the back is genius as that's where I always have a finger as opposed to the front. It's so awkward to try to hold the phone in my hand securely AND holding my thumb on the scanner at the same time.
About half of the times i unlock my phone is when it is resting on the table. Fingerprint scanner on the back requires picking it up first, which is extremely uncomfortable to do every time. No. Just no.
I'm glad we have choice then.
I agree, but for a different reason. Today's phones are stupidly fragile and pretty much everyone puts some sort of case on them. I don't get this obsession from phone makers to make increasingly thinner devices, when a large number of end users just put an ugly case on it. Why not make them rugged to begin with?
Would you really rather that rubber/plastic of the case was fused to the phone instead of just separate and replacable?
I'm sure Apple can design a rugged phone if they wanted to. A rugged phone designed with shock/vibration/drop protection in mind is not the same as a fragile phone with a case on top.
All kinds of ruggedization are wear items. Even a bicycle helmet needs to be replaced after it has experienced an impact. They should be easily replaceable, like phone cases are now.
There are many designs possible, I don't understand why you want to shoehorn an unsuitable design meant for providing protection to the human head onto electronics. In any case, this is a good discussion, we know what to avoid so yes - we don't want to have a design that necessitates replacing the phone.
I've always found that unlocking your device with your fingerprint scanner on the front of the device only works nicely if you're holding it with the other hand.