Piracy is convenient.
Downloading - a few minutes of my time to start the download. Then after it finishes (which is very fast usually), I can watch the movie on whatever device that has enough processing power and a screen, at any time having full control of it.
Going to the cinema (in general) - need to drive to wherever the cinema is, at a specified time, watch it with a bunch of strangers (that may include screaming children), no control whatsoever - cannot pause the movie to go to the toilet, cannot rewind a few seconds to rewatch a scene I missed, cannot increase or reduce the sound volume, cannot even have a conversation with whoever I came to watch the movie (assuming I did not come alone) during a boring part. Forced to watch ads before the movie. Cannot bring the food that I want (that is not sold (at high prices) in the cinema). The movie has to be recent enough to still be showed in cinemas.
Going to the cinema (this particular movie) - All of the above but include traveling to the US, getting a hotel room etc.
Buying a DVD/Bluray - Better than going to the cinema, but still have to go to a store that sells them, have to sit through a bunch of unskippable ads.
Time from "Hey, let's watch a movie! Which one? [googles some previously unheard of movie] This one." to actually watching it:
DVD: 30 minutes - 1 hour (assuming the store is open), days (if the store is closed).
Cinema: 30 minutes - 3 hours (assuming the movie is being shown in cinemas and the cinema is open), days (if the cinema is closed), undefined (if the movie is not shown in cinemas).
Download: 5 - 30 minutes (my internet connection is up to 500mbps).
Oh, and Netflix is not available in my country in case you were going to suggest it.
So, see, even if the tickets for the movie (or the DVDs at the store) were given away for free, downloading would be the preferred option.