There's a few things I want to enforce internally.
Save us from having to communicate these things in PR reviews.

ensuring people don't do import ts from 'typescript' in packages.
this breaks compat with users that don't use allowSyntheticDefaultImports
ensuring people don't accidentally do import {} from '@typescript-eslint/typescript-estree' from the plugins, where the package isn't a dependency.
this breaks encapsulation, and will cause problems if we move things around in future
Adding this in now reduces the barrier to entry, meaning we can easily add rules to warn against patterns we see people do in the future.