Steve Jobs drew his own red-line over 7 inches being too small for tablet, due to the size of hands. I've heard that parroted back at me by apple fans a few times. This is why the ipad-mini is decidedly not a 7" screen, but an 8" (7.9) screen.

Here's Tim Cook still talking about how horrible 7" tablets are in 2012. http://techcrunch.com/2012/10/25/tim-cook-we-will-never-make...