There are some cases where formatters like Prettier don't have one canonical representation for an AST, in particular behavior around line breaks (multiple empty lines are allowed, a line break after an "{" opening brace in an object literal will force it to span multiple lines, etc)

But yeah, otherwise everyone could just have their own preferred formatter/settings and we could commit whatever representation is most optimal for diffing to version control (e.x. multi-line object literals, trailing commas in arrays/args, etc).

You could use something more compact like a binary AST but for compatibility with "legacy" tools that deal with text I think it would be better to use a more verbose text-based representation.