"To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries." - Article 1, Section 8, Clause 8 of the United States Constitution
This is a pandering quote which everyone already knows and not really a useful comment at all.
Even here on HN, I've seen posts from people who think patents are intended as a reward for inventors, rather than an incentive to invent. Under US law, inventors and writers do not automatically deserve exclusive rights - those rights are granted only as a means to encourage progress.