Why is C++ AI used more than python?

You don't need a powerful language for programming AI. Most of the developers are using libraries like Keras, Torch, Caffe, Watson, TensorFlow, etc. Those low level libraries are highly optimized and handle all the tough work. They are built with high-performance languages, like C, C++. Python is just there for high level tasks like describing the neural network layers, load data, launch the processing, and display results. Using C++ AI for high level tasks instead of Python would give barely any performance improvement, but it would be harder for non-developers as it requires care for memory management. Also, several AI people may not have a very solid programming or computer science background. Another similar example would be game development, where the engine is coded in C/C++, and, often, all the game logic is scripted in a higher-level language.