Very short answer: because a treesitter will do an approximately correct parsing, while a hand written parser will do a correct parsing (and if not, it is a bug

Very short answer: because a treesitter will do an approximately correct parsing, while a hand written parser will do a correct parsing (and if not, it is a bug). For a full, balanced overview, see: https://blog.jez.io/tree-sitter-limitations/ https://blog.jez.io/tree-sitter-limitations/