It's a tradeoff. Some markets require large research investment up front (like pharmaceuticals) and they won't bother if others can immediately sell the same f

It's a tradeoff. Some markets require large research investment up front (like pharmaceuticals) and they won't bother if others can immediately sell the same finished product without doing the research. Without patents you also get trade secrets which can leave the public without ever knowing how something works. Patents are an attempt to exchange a limited time monopoly for a complete disclosure of how the invention works so that the public can benefit. There might be an argument for that time being too long (and I think it's completely broken when it comes to software), but I can see why they're useful as incentives.