Apple isn't leading the way if you're talking about mobile phone sales. They were leading a niche of the market. Last I saw, indications are that Samsung had even outsold Apple in the smartphone segment last quarter.

And if you think all TV's nowadays look the same I don't think you've seriously shopped for a TV. Yes, the overall shape is the same, but there's a wide variety of designs within the constraints of utility. By constraints of utility I mean that all TV's look similar because we all want a screen that is suitable for existing programming and that means mostly 16:9 format, and it is impractical to have a TV that protrudes in all kinds of directions beyond the screen itself, so the overall design is limited to a 16:9 screen plus a reasonably narrow frame. We also don't generally want bright colors because it is distracting.

It is similar for mobiles - it is limited by weight and size constraints tied to our desire to carry them in our pockets and hold them in our hands, while having a large displace.