Only building dist for ESM modules?

[Shubham Paliwal]

I have seen the dist of @artsy/palette package.
Have Following question?

• Why we are not building package in other module like UMD.
• Why we are using babel if we can compile it using tsc and it will produce the same lib.

import {abc}  from 'xyz';
import abc from xyz/dist/abc

did both the line will do the tree shaking ?