Why can’t swift playgrounds be on iPhones too?

>Why can’t swift playgrounds be on iPhones too?

Because Apple needs more help selling iPads...seriously.

And given this has an educational component, it helps support Apple's continued push for iPads into that market. If Playgrounds were suddently supported on the iPhone, it would undermine those edu-centric efforts overnite.

See this link and notice that except as an end-user platform, Apple isn't marketing the iPhone in an edu context:

https://www.apple.com/education/products/

I don't think iPhone has enough screen real estate to be useful for development work. That's my guess. Of course you're never going to get an actual authoritative answer to that question - Apple doesn't generally discuss their marketing / roadmap plans for features like that.