Many people watch movies online on illegal sites because they can't find a proper legal channel to watch the movie on.
Some legal apps such as Netflix and Amazon Prime might not contain all the movies a person wants to see. In such a case, the person might decide to stream the movie from an illegal site. See why Netflix has very few movies.
Some people choose to stream movies online illegally because they don't want to pay money to stream a specific video.
Some legal streaming services such as Amazon Prime doesn't work in some countries. People in those countries might have no option but to stream a movie illegally.
Most new movies usually don't make it fast to the legal streaming apps and services. In such a case, a person might not find a way to watch the movie but to stream it online.
Some movies might not reach theaters in some countries. In such a case, people might find no way to watch the movie but to stream it online illegally.
In some countries, there are no strict laws for streaming illegal content online. In such countries, illegal streaming becomes more of a cultural habit than a crime.
Some people stream movies online because they don't have credit cards that would allow them to subscribe to a legal service.
Unlike the music industry where a person can find almost everything on legal sites, the movie industry is still very protective and tries to delay the release of movies on the internet as much as possible.
If a person has no access to theaters or if they work in a remote area, they might stream movies illegally.