True, economically speaking personal use value doesn't really matter. It's great for you, but economics is about exchange.

Enforcement is an interesting factor. Laws can guarantee rights to enable and protect free exchange, but they can also coerce behaviour as I touched on.

In more or less free markets what laws do is provide guarantees that increase trust, which has the main effect of reducing costs. You don't need to personally audit the books of a company you invest in, because the government mandates that it's done for you to a set of standards which eliminates some risks (not all, just some). You don't need to personally research if the products you buy are safe or of a basic level of quality if the government mandates standards and enforces them, and if you have a right to return goods if you find a problem with them. This makes the goods themselves a little more expensive, but the overall costs and risks (which translates into costs) to consumers are much lower.