I linked the law earlier - you replied to that post. Did you click the link? The law is a much MUCH more complicated than that.
https://www.law.cornell.edu/uscode/text/17/506
So, we have a list of 3 ways to be criminally punished for illegal downloading, any one of the following is sufficient:
(A) gain a commercial advantage or some kind of financial profit.
So, if a person is not selling pirated material and isn't using it for any commercial purpose at all, then this doesn't cover them. The prior cases are pretty clear, not paying for something is not private financial gain. Prosecutors have to show actual profit to prove this.
(B) reproduce or distribute copyrighted stuff worth more than $1000 in a ~6 month period.
The value here is commercial value. So if a person is downloading MP3 singles, that's like 600 songs, or 60 songs per month. If we're talking movies, that's like 25 movies or so, or 4-5 movies per month. It could also be 1 copy of some crazy software suite, or it could be 100,000 cheapo ebooks. It's not at all hard to stay under this limit. I'd wager the majority of casual torrenters stay well under this limit.
(C) distribute copyrighted stuff over the internet before it's officially released.
This pretty much just covers leakers, people that work at studios or distribution who leak stuff online before it's released. Again, very small crowd.
And on top of that, you have to prove the reproduction or distribution was willful! "Evidence of reproduction or distribution of a copyrighted work, by itself, shall not be sufficient to establish willful infringement of a copyright." Absent a clear paper trail, it's pretty hard to show willfulness.
So as you can see, the current status is far from simple. And the current copyright statutes do not cover any criminal punishments for what most consider casual internet pirates. That other dude I replied to who talked about his brother seeing his music downloaded on torrents - most likely those people would not be punishable under the law.
It's a complicated issue, and it shouldn't be reduced to unworkable analogies such as theft or stealing. It's very different.