Look at the Design
What does it tell you? The design on screen is very plain: you can pick up the phone, make a call, write a note of some sort, do a thing that involves squares, see the globe (Internet), and take a picture.
The two ends of the phone are taken up by stereo speakers. Probably sound pretty good.
So... where does the fingerprint device go? You can't say, "Just jam it in between the icons, or under the icons and above the speaker. Well... no good. Cluttered. You'd hit the other icons half the time. Suddenly, you phone somebody or write a note to someone that says "konihhgwlllwz". No good.
Where? Where, except where there's been a hardware button since 2007?
I think they realized at some late point in the design phase that Apple was putting touch ID on their newest deluxe phone, so they rushed it through faster, way faster, than they should have. It's better to wait until you have it right, HTC. Release a new phone that doesn't have the feature, and then a phone that does, whenever the feature is ready. Don't worry! The Android press will say, "Who needs it?" until they have an equivalent implementation, when it's "Android gets it right!"