I recently bought a phone that's so large it takes both hands to operate it. If I'm grasping it reasonably tightly, my thumb can't navigate to over 30% of the screen. If I stretch uncomfortably to try to reach those areas, the phone is likely to slip out of my fingertips entirely. I do not have small hands.
I'm not sure what the market standard definition of "phablet" is, but for me, a 136mm x 68mm device has served me fine for years, and this new device (which I'm returning after almost accidentally throwing it across the train for the n'th time in as many days) is 148mm x 76mm. Apparently that extra ten millimeters is a big deal. (Interesting to look at Apple's product page for their sizes. They measured this too, evidentially -- the 6 and 6s went up to exactly 138x67 and aren't budging; they use the Plus series to probe over that line.)
The fairphone2 is 143x73 -- it's not as big as some other flagships on the market right now, so huge kudos for winning the miniaturization battles so far -- but I bet they're falling prey to competing on screen size, and frustratingly, though I'm interested in everything else about this phone, I'm honestly not sure I'll be able to hold it in my hand.