std::vector<bool> is just a terrible specialisation, it isn't an optimisation.

If std::vector<bool> was an optimisation we couldn't write C++ which blows up because it's actually a bitset, it would be semantically transparent - but that's easy to do even by accident because it's not transparent at all.

In fact the existing std::vector<bool> should just be named std::growable_bitset or something and then std::vector<bool> would make what you actually wanted like Rust's Vec<bool> does.