Why Machine Learning is not Artificial Intelligence?

It is simple: because ML is only a contributing branch of AI. If we follow Norvig and Russell book -and other authors-, saying that machine learning is equivalent to artificial intelligence is grossly misleading. ML is a contributing discipline of AI, just like search, reasoning, planning, decision making, natural language processing, vision, and robotics. For instance, ML by itself cannot be intelligent because lacks reasoning, planning, logic, and doesn't interact with the environment. ML detects patterns and performs predictions based on statistical analysis of data using math based algorithms. These algorithms are not intelligent per se.