Its cause they’re all pocket computers that just happen to be a phone too.

Even this phone only mobile phone from punkt still has that form factor so it can fit in your pocket.

I saw a toddler pretending to take a phone call from an imaginary phone a few weeks ago, and it really threw me that she was holding her “phone” like one would a smartphone (As opposed to putting your thumb to your ear, and outstretching your pinkie towards your mouth).