I think it's because CLion is a bit of a separate codebase, integrating with GDB and all that, rather than just a language plugin that's also sold as a separate

I think it's because CLion is a bit of a separate codebase, integrating with GDB and all that, rather than just a language plugin that's also sold as a separate IDE as is the case for other languages. This is also why the Rust plugin only has proper debugging capabilities in CLion.