Why would anyone ever want the fingerprint reader under the front screen when it works so well on the back? Why do people want glass on the back of their phones when it breaks so easily? Some trends really don't make sense to me.
makes perfect sense if you are trying to sell new phones. otherwise, for the customer, it's something like "I can pay several hundred dollars to have a phone exactly like the phone I already have, or I can pay nothing and keep the phone I already have. hmmm...."
so, they make changes. all the time. for no reason. because they want more money, and a certain percentage of people are going to be drawn in by any given feature, even if it's a crappy alternative to an existing feature.
this isn't rocket science.