That's right. But they are able to have what we call a shared experience, which is a little different. However it isn't relevant here, because the shared experience of all the employees of a corporation is not the basis for the legal personhood of corporations. And what is the basis?

class Corporation : public Person

It's for the same reason mediocre OOP programmers use inheritance to borrow some partial implementation. It gets the job done, even if it doesn't quite fit.