The goal of prettier is not to format code exactly as you would have written but to format it in a reasonable way. The upside is that as a developer you don’t

The goal of prettier is not to format code exactly as you would have written but to format it in a reasonable way. The upside is that as a developer you don’t need to worry about formatting yourself as you can just write code in a bad way, save the file and it’s formatted. And as a team, you will no longer spend any time in code review arguing about formatting and doing roundtrips to change small nits. If the result is good enough that you are willing to let go of your manual formatting, the upsides are nontrivial.