[Calavar]

You mean different purposes by humans or different purposes by machines?

For machine manipulation, I think it makes more sense to directly manipulate the AST.

For human manipulation, I think the cognitive overhead of mentally converting between the display syntax and the canonical syntax would far outweighs any gains in readability. But maybe your workflow is different than mine - If you have a lot of custom macros in your editor, I could see s-exps being useful (although, again, I think exposing and directly manipulating the AST would be less error prone)

[fiddlerwoaroof]

A programming language doesn’t need a canonical syntax if its semantics are specified in terms of the data-structures the parser produces and not in terms of the textual representation of those data structures.