The only justification for the real system was that it worked

How Much Does File Sharing Resemble Stealing--And Does it Matter? by Megan McArdle.

But of course, no system of property rights is built from first principles. Nor did property rights spring full-blown from the head of Zeus at the dawn of the universe. It's a highly contingent system that evolved over centuries, with all sorts of weird principles that we'd never have thought of if we'd been designing the thing from scratch. (For example, read the chapter in Moby Dick about the system for allocating rights over hunted whales. A lawyer once told me that in law school, his class was assigned to come up with a system to solve the problem. No one came up with anything that looked like what actually evolved; the only justification for the real system was that it worked.)