Nobody wants thick phones, e.g. like bricks. But you can get away up to a certain extent with thin phones. In the pocket, a thick slider phone with a smaller screen will bulge out more than a touch screen only phone with a large screen but with a very thin profile.
Just for anecdotal record, I talked to a lot of middle aged and older people, and for them a large screen phone with a display that they don't have to squint at is most desirable. Considering the growing aging population worldwide, this is of demographic importance. This is more than just a "fashion trend", larger screen phones are here to stay and is going to be more common in the future.
Another demographic factor is the increasing obesity with people, especially among the middle and older aged. This means thick fingers, and you need bigger screens and so on. I am not suggesting that we go extremes like the Japanese Sumo wrestlers being issued iPads for phone calling (true story!) but you get the basic idea.
