std::map and std::unordered_map are just unbelievably shitty implementations. The former is a red-black tree, which in my entire programming career I have needed to reach for like... twice? It's just not the right container for almost any problem you have, yet it's the one that gets the short, sweet name. The latter is a bucket-based hashmap, which is about the worst kind of hashmap that can be built. On top of that, their APIs are also really annoying to use compared to, say, Python or Rust's implementation. At least C++20 finally added a simple contains method, but something like setdefault is just a chore to get implemented.