Allocators were well intentioned, but writing them is not a walk in the park, and you cannot pass, say, a “std::vector<T, my_allocator<T>>” to a function expect

Allocators were well intentioned, but writing them is not a walk in the park, and you cannot pass, say, a “std::vector<T, my_allocator<T>>” to a function expecting “const std::vector<T>&”.