Here is the reality: Animated films like Son of Batman have small budgets compared to live-action blockbusters. When you pay for the movie (or stream it legally on a service like Max), you signal to Warner Bros. that there is demand for more adult-oriented, faithful DC animated adaptations.
Additionally, subscription-based services like Netflix, Hulu, and DC Universe offer a vast library of movies and TV shows, including some Batman-related content. While "Son of Batman" may not be available on these platforms, they provide a great alternative for accessing other Batman movies and shows.