Prettier is not a kitchen-sink code formatter that attempts to print your code in any way you wish. It is opinionated. Quoting the Why Prettier? page:
By far the biggest reason for adopting Prettier is to stop all the on-going debates over styles.
The more options Prettier has, the further from the above goal it gets. The debates over styles just turn into debates over which Prettier options to use.
The issue about resisting adding configuration has more 👍s than any option request issue.
So why does Prettier have options at all?
Then there's a bunch of interesting cases.
--trailing-comma es5was added to make it easier to use trailing commas in most environments without having to transpile (trailing function commas were added in ES2017).
--prose-wrapis important to support all quirky markdown renderers in the wild.
--arrow-parenswas added after huge demand. Prettier has to strike a balance between ideal goals and listening to the community.
--jsx-bracket-same-linewas needed for a big company with a huge code base (Facebook), which backed the project when it got started, to be able to adopt Prettier at all.
Finally, perhaps the most interesting of them all is
The truth is that not even Prettier's creator knows exactly why it exists. It was added super early on without much thought. It now serves as an example of the types of options we should avoid.
Remember, it is easy to add features to a program, but hard to remove them.