Most likely because last time a takedown case went to them, they ruled that it was a violation of the First Amendment to take down some unrelated content (stuff on the same IP block if I recall) while shutting down a child pornography website. People hate pedophiles even more than media pirates, as a rule, so I'd guess they'd rule in favor of free speech here as well.
This. Also, a court is competitive, with evidence for both sides etc, while there's no such thing as "counter-lobbying" in the Congress.
Referring, of course, to the proposed U.S. legislation which could cause severe damage to the Internet—at least, that's what a lot of people are saying. See, e.g., this Open Letter From Internet Engineers to the U.S. Congress (the first signatory listed is Vint Cerf). On Wikipedia, people including Jimbo Wales are discussing strategies as extreme as blanking the entire site (except for an explanatory message) to get people's attention, and thereby perhaps incite them to action, such as calling their Congressional representative.
I just happened to find out about all this a few hours ago, being someone who tries to avoid distractions like most kinds of news, so possibly others here with similar habits will appreciate having it called to ther attention. Or possibly they won't. But to those of you who possess relevant kinds of expertise:
(I think this subject can be discussed without political advocacy, in which I am mostly not at all interested anyway. It just looks like a practical problem to me.)
Edited to Add: I forgot to include a fourth bullet point:
It seems to have been assumed by many commenters, nevertheless.