Nowadays people think of patents as a way of protecting the "property" of inventors, and so patents are granted and enforced according to that principle, regardless of whether they promote or hinder progress. The usage of the words "theft" and "piracy" to refer to patent and copyright infringement is a symptom of this state of mind.
Thomas Jefferson et al would have called this nonsense. By its very nature, an idea -- once divulged -- cannot be someone's property, and it should not be treated as such. To prevent the free flow of ideas through a populace is, in many cases, harmful. (Imagine a group of hunter gatherers in which one family has patented the idea of farming.) At most, limited monopolies should be granted to prevent situations in which nobody is incentivized to create due to rampant copying. But we still have to be judicious in granting these monopolies:
"...it may be observed that the nations which refuse monopolies of invention
are as fruitful as England in new and useful devices."
-- Thomas Jefferson
"But grants of this sort can be justified in very peculiar cases only, if at
all; the danger being very great that the good resulting from the operation
of the monopoly, will be overbalanced by the evil effect of the precedent; and
it being not impossible that the monopoly itself, in its original operation,
may produce more evil than good."
-- James Madison
It's painful to see copyrights and patents today accomplishing the polar opposite of what they were intended to. But we've been gradually heading in this direction for the last 200 years.In my opinion it's a combination of (a) allowing businesses to have too much say in law-making, (b) Congress + the populace not being sufficiently educated about the implications of copyrights and patents, thus giving more power to the natural tendency to think of ideas as property, and (c) the Supreme Court following overly non-interventionist policies and allowing Congress to make unconstitutional decisions.