It does indirectly come from age, because legacy and backward compatibility mean that you can't simply change some core parts of the language at all. For instan

It does indirectly come from age, because legacy and backward compatibility mean that you can't simply change some core parts of the language at all. For instance, std::optional uses UB because _all_ of C++ does the same, and making std::optional<T>::operator* different from std::unique_ptr<T>::operator* would have caused similar concepts to have a different behaviour - something that would have definitely translated into weird bugs. Also, C++ hasn't features like built-in move semantics and borrow checking, so it's very hard to enforce certain things that just come natural in Rust. That's simply stating a fact. The real point here is that std::optional<T> is much less likely to cause UB than a plain, old C pointer, so it's a net improvement - even though it could still lead to UB in some circumstances.