Try getting out of the iPhone bubble for a while - you'll find that in the real world, phablets are not just something that you make fun of.
My phone is just on the edge of one-hand usability (I can mostly manage it but sometimes things get pretty awkward) and I often wish I had something iphone-sized instead, but choice is pretty limited among smaller Android phones (they exist, but tend to be old/slow/etc).
People I know with phablets use them like tablets (almost always with two hands etc). That's fine if you want a small tablet, but it isn't really an adequate replacement for a traditional smartphone. They're just different things.
E.g., I see huge numbers of people standing on the train using their phone with one hand (while hanging onto a strap with the other) or walking down the street, using their phone with one hand (while carrying a bag with the other), etc.