For me, going from a 4S to a 5 was a little problematic due to the length of screen. When in bed particularly, and many times otherwise, I would accidentally hit the back button (excellent touch response, Apple). I took a 5s last November, for few reasons.
1. While driving, it is easier to handle a 5s single-handedly.
2. I wanted a phone and understood the restrictions (there is no end to wanting larger screens, right?)
3. Portability is a huge plus.
The only phone that I can replace this with is a 6. I cannot use a 6+, first of all I don't like that big a phone, it looks like a slap on the ear overtime you use it (to me) and secondly due to my hand structure - don't have large hands. 6 is the maximum I can take in a phone. I have always been able to differentiate between a phone and a tablet and a computer screen. All have their uses. And in some ways, it is much better to use all of them.
Using cellphone at home to browse can be avoided if you have a tablet. Using a tablet means you get a larger screen plus don't get the very harmful radiation of cellular towers. So on. It is about effective and efficient use of technology, not just cramming and converging everything into one device, mindlessly - hence a phone, a larger phone, an even larger tablet, and now the super large iPad Pro.