I imagine because Swift famously touted the ability to use emojis as identifiers.

Reading these things makes me hungry.

I think it’s because that’s the style of Apple’s own (excellent) Swift Programming Language book.

I think it does look nicer than the traditional characters used in these kinds of things.

The language supports emojis, and the point of example code is to be as concise and easy to understand as possible. Better than foobar.

Easy, our mobile devices screen width is limited. Emoji is the idea and it make learning not boring.