Think about it as the difference between only inheriting functionality (interfaces in Java 1.8+, Rust traits, etc) vs inheriting data. OOP can become spaghetti

Think about it as the difference between only inheriting functionality (interfaces in Java 1.8+, Rust traits, etc) vs inheriting data. OOP can become spaghetti very quickly. Especially as people mistakenly allow children to modify parent memory directly, protected non-final fields in Java. Once that happens and as the inheritance higherarchy gets deep, understanding what a field actually is at any point becomes very difficult. Interface and trait inheritance at least removes one piece of confusion by only allowing functions to be inherited, which makes code much easier to reason about.