> you can highlight a binding if it’s mutable or style an enum/struct differently

Wow! That is an incredibly good reason. Thank you very much for telling me something I didn’t know. :)

UPDATE: I've added a paragraph talking about the ability of rust-analyzer. Thank you again!

Another pretty common application is to color unused bindings with a slightly faded-out color. So for e.g. with the TypeScript LSP, up at the top of the file you can instantly tell what imports are redundant because they're colored differently.