It was discussed at length at the time on different podcasts such as ATP and The Talk Show, and I recall it was the case mostly in Asia.
It had to do with the perception of the physical button's flimsiness and unreliability. And was coupled with the far different experience in regards to Apple Repair centers (sometimes not even provided by Apple itself) which made the whole experience an ordeal. So, to preserve the value of the phone, they preferred the software button instead.
Others chimed in to say that, other than having to deal with repositioning the button from times to times because it obscures something below, it was actually a step up in usability as it offers more options (there is a whole user configurable menu there).
Why they continue to do it after the 7's fake hardware button? Probably because of the latter cause.
It had to do with the perception of the physical button's flimsiness and unreliability. And was coupled with the far different experience in regards to Apple Repair centers (sometimes not even provided by Apple itself) which made the whole experience an ordeal. So, to preserve the value of the phone, they preferred the software button instead.
Others chimed in to say that, other than having to deal with repositioning the button from times to times because it obscures something below, it was actually a step up in usability as it offers more options (there is a whole user configurable menu there).
Why they continue to do it after the 7's fake hardware button? Probably because of the latter cause.