1. Inheritance is about extensibility. You won't encounter suitable applications in self-contained toy universes where you can almost always rewrite something as some form or another of a typecase statement (whether that's Pascal-like variant records with case statements or ML/Haskell-style pattern matching). See also the expression problem [1].

2. "Inheritance" itself is a fairly fuzzy concept. Do you mean implementation inheritance (for code reuse), polymorphic subtyping (for polymorphism with late binding), do you account for virtual types, etc.?

[1] http://c2.com/cgi/wiki?ExpressionProblem