Why don't I make the physics module myself?

I will not do it because following research, I have found how advanced physics engines have become and how a lot of great engines exist.
It would be wasting too much time for me as a sole developer to try and learn about this process myself.
I will however do tests to understand the underlying process behind the engines but I won't try to implement\ an optimized version of every process, the engine I will import will have the optimized functions.