If you're looking for a tablet that will replace your laptop, then you'll probably want something that has a 10 to 12" screen and attach a keyboard. However, if you're like a growing number of people who are using a smartphone, a laptop, and a tablet, then the 8" form factor is the ideal size. That's what I've found whether I'm working in the office, traveling, or catching up on emails and reading articles at home. I don't attach a keyboard to my 8" tablet. If I need to do that much typing, then I'd rather pull out my laptop.
Medical students and residents wearing white coats in the hospitals will also tell you that most 8" tablets fit nicely in their white coat pockets. No pocket modifications required.
As more people start switching to monster-size phablets instead of smaller smartphones, the role of the 8" tablet could disappear since larger phablets like the Galaxy Note 4 or iPhone 6 Plus offer plenty of productivity space on the screen.