The point is every bit of software is vulnerable and it's not helping anyone.

If your "invention" could be recreated by another programmer independently, often inadvertently, it's not really much of an invention now is it?

So by that argument, the invention of calculus was not a big deal, since Newton and Leibniz arrived at it independently.

Calculus was discovered, not invented.

What's the difference?

If there's only one way to do it, and anyone faced with the same problem would have to do it the same way, it's a discovery. Otherwise, it's an invention.

Inventions are patentable. Discoveries aren't. Or shouldn't be, according to the intent of the system.