Attention isn't the issue. The issue is holding your phone directly in front of your face while it unlocks, which is far different from TouchID. If I'm using Apple Pay, I double tap the home button while it's still in my pocket and then wave it past the reader. At no point do I look at my phone.

Likewise if I'm checking the time or a text message, I'll hit the button with my finger while the phone is laying flat on the table. But that use case doesn't exist anymore either.

Unlike a computer screen, phones are not always pointed directly at our faces all day. It'd work fine to unlock my Macbook, but not my iPhone.