Apple CarPlay on a iPad?

Whilst iOS for iPhone and iPadOS for iPad are closely related, there are many native functions, features and Apps that are only available on one or other of the two related - but different - platforms. As for why Apple choose to make some Apps available to iOS for iPhone, these decisions are not shared by Apple.

The CarPlay feature - Health, Calculator, Translate Apps - are not elements of iPadOS for iPad.

If you have strong feelings, Apple invite constructive feedback and feature requests via their product feedback portal:

Product Feedback - Apple

You'd have to ask Apple.

We are all just, largely, Apple product users here, just like you.

You can send unacknowledged product feedback to Apple here.

Feedback - iPad - Apple