Interesting is how it is all about preference... 7" tablet is too small for me, but it is way too big for phone. Then there's Kindle in this screen size category

PS: I think the only reason screens sizes are currently growing is the fact that phone manufacturers are lost and don't know how else to innovate. All smartphones look the same, regular customers don't care how many cores the CPU has, further addition of megapixels to small cameras turned counterproductive... Right now, making bigger screens is the only way to emulate innovation for marketing.