Re: This is for several reasons
"I can hold it in my hand" is a pretty compelling USP.
I originally got a 7" Samsung tablet to give to my kid but the wife took it instead. She replaced her iPad with it. It's big enough for her requirements plus it is more portable. It's good enough while being small and cheap.
She dumped her iPhone for an S3 too. Got tired of waiting for the iPhone 5.
A 7" tablet is cheap enough to be an impulse buy, an Apple tablet not so much.