Subclassing can suck. There are so many ways to get it wrong and it's so easy to fall into anti-patterns when you create such a tight coupling between two classes. Most of the time, the need for subclassing can actually be replaced by abstraction through protocol-oriented, value-oriented, and functional programming. In fact, I may even argue that doing it that way can far outweigh the "benefits" of subclassing the majority of the time.