How?

Contract law has evolved because transfering the ownership of things is fraught with difficulty. Ownership as a concept itself is notoriously hard to define.

Consider housing - when you buy a house you own that land. Except if its an apartment, you just own the internal walls. Or when the government aquires your land through eminent domain. Or mineral rights - which don't belong to you, you just own the top 5 feet of topsoil. Or if you neglect a property and some squats in it. Or if you were given a fraudulent payment, and they take back the property.

Just getting people to agree is notoriously difficult when people have different often conflicting desires.

Most people dont appreciate that the world is a complex place. Nothing is ever simple, sure concepts can be extremely simplified but the nuances and details are lost. These details are the important parts, just ask a surgeon or rocket scientist etc.