The market has spoken and there is something about them that the majority of consumers want. Personally, although I wouldn't want a small smart phone and appreciate a thickness that provides a good grip, I would be quite happy to see the tech get just a bit lighter.
Most of the size and weight is probably the battery. Personally, I think screen sizes have gotten too big, but that is just my opinion. Most Samsung devices are too big for my preferences, and that's one reason I don't buy them.