I just learned that you can actually download an entire website using programs like httrack or IDM, what stops people from using these programs to download the whole Netflix library for example, and never pay for a subscription, it shouldn't be that easy so can someone tell me what's the catch?
Movies and shows are basically stored in separate servers/departments, and downloading just the HTML would not give you access to any of the other files. Think of it as viewing the page source for any other website, like even StackOverFlow, you cannot view the CSS, javascript, or any other files of it. You are only able to see the HTML.
BTW as a heads up, this is not a quality question and does not meet the guidelines of StackOverFlow, I would suggest you ask these type of questions in the communities of StackOverflow.