If I buy a washing machine......they pretty much all look the same.
If I buy a TV.........they pretty much all look the same......a black rectangle, but with a different company logo on it.
Smartphones all pretty much look the same, since they're almost all screen. GPS units pretty much all look the same, and you don't see lawsuits among them.
A tablet is a hand-held screen. It's basically a rectangle. Not much to improve upon, or to differentiate...