If HTC don’t use on screen buttons, there is still other buttons which take up space. You can have a look at how those “buttons” of GS4 take up space. If you exclude the speaker of HTC One, the space that is used for “buttons” is pretty much the same between HTC One and GS4 (may be 0.2 cm differences).
The problem here is Microsoft doesn’t want people to buy those “plenty of W7 Pro on PCs online from Dell and others”. Microsoft wants people to buy Windows 8 PC. Therefore, Microsoft has no choice but do something about the request of “old Windows 7 stuff”.
The problem here is MS force people to use Touch-centric OS on PCs which do not have touch screen.
It is totally fine for Metric UI to be used on touch screen. However, Metro UI is rubbish when we are using a non-touch PC. It is not funny for many people who operate the Metric UI through a track pad (or even the red dot on Lenovo laptop). Geeks may not mind learning how to use track pad or red dot on Metro UI, but normal customers really mind about wasting their time and effort on such kind of things.