I need to Understand that whether really Inheritance & virtual functions not necessary in C++ and one can achieve everything using Generic programming. This came from Alexander Stepanov and Lecture I was watching is Alexander Stepanov: STL and Its Design Principles
Polymorphism (i.e. dynamic binding) is crucial for decisions that are based on runtime data. Generic data structures are great but they are limited.
Example: Consider an event handler for a discrete event simulator: It is very cheap (in terms of programming effort) to implement this with a pure virtual function, but is verbose and quite inflexible if done purely with templated classes.
As rule of thumb: If you find yourself switching (or if-else-ing) on the value of some input object, and performing different actions depending on its value, there might exist a better (in the sense of maintainability) solution with dynamic binding.
Some time ago I thought about a similar question and I can only dream about giving you such a great answer I received. Perhaps this is helpful: interface paradigm performance (dynamic binding vs. generic programming)