system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we need patents?
gpt
First point to understand is that it is way easier to make something than it is to come up with the idea to make it. 

People and companies often spend a lot of time and money thinking,  modeling,  prototyping, testing,  rethinking, etc before they come up with something people like enough to buy. 

The government has decided that it appreciates this time and effort.  That because of this time and effort,  the public gets to have lots of cool stuff.

But there is a problem.  People go through that effort and invest the resources in large part because they think if they do end up worth something that the public wants,  they will be able to sell it and make money for themselves and their family or their company. 

But remember point one.  The hard part of most products isn't making it,  it's coming up with it.  Without patents, people would just wait until an invention happens,  buy one,  make lots of copies, and undercut the original inventor (after all,  they don't have to make up for years of investment cost, so they can sell them cheaper. 

If that happens too much, the government fears people will stop inventing. 

At the same time,  one of the ways society progresses us improving on other people's designs. 

So. .. patent us the compromise.  The government says "you tell us exactly how your product works,  we will make sure nobody copies it for a few years,  and in return,  when your time is up,  society can take your invention and tweak it to keep us progressing.