There are a lot of people who don't want a bigger screen. (but there are quite a lot who want enormous screens)
I was one of the people who didn't really want anything larger than 4". Then I changed my mind over the past two years. Want to know what really changed my mind? The Moto X. I never owned one, but it was the first phone I saw in the store with a larger screen (more than 4.5") that felt relatively small. I was really amazed by how much the experience of a large screen could be improved by slimming down the device and bezels.
See, when most of these people were complaining, myself included, 4.3" was a huge screen, and it was found on phones like the EVO 4G, which WAS a flippin' monster of a phone. It was nearly DOUBLE the thickness of the iPhone 6, with big bezels and buttons, and it felt like a brick. In fact, it's essentially the same weight as the iPhone 6+, but with a screen 1.2" smaller.
However, over the past few years, the technology has enabled larger screens in slimmer and more compact devices. After playing around with some, and using my iPhone for more and more web browsing, I began wanting a larger screen.
For me, 4.7-4.8" is about ideal (at this time). It's small enough that I can still do most things one handed, but large enough to provide a nice bigger view. The 6+ is just too big for me right now, and it's the reason I ordered the 6, even though I'd have liked the larger battery and OIS. (the 1080p screen doesn't matter much to me, honestly).
I could see myself going to 5" if the bezels are shrunk properly, but I don't see enjoying much larger than that for a daily carry phone, though people's tastes change over time.
When my 6 case came today, I was very glad I didn't go for the 6+. The 6 is definitely a big phone anyway, and about at my limit for comfort.