Using Movies4uFreenet is generally due to the high risk of infecting your device with malware. If you are looking for free, legal alternatives, platforms like IMDb often provide "Where to Watch" guides for legitimate free-with-ads services like Tubi or Pluto TV.
Because these sites operate without licensing, they cannot rely on legitimate ad networks like Google AdSense. They rely on "malvertising" networks. Here is what happens behind the scenes when you click play on a site like this: movies4ufreenet work