I saw the movie "Seven" on Netflix about a year ago. He was unfortunately removed before I saw him. Now I saw that he was added again. Why does Netflix do that? Is there any rule that films should not stay long or something?
(in series, I have never seen that they were removed)
That's because of the licenses. Netflix needs to buy licenses for movies and series that are not Netflix originals. If the licenses expire, the items fly out of the program. I think, since the customers can also want movies and series, then it is decided which license is bought again or new. Therefore, it can happen that something that was not in the meantime on Netflix was back there.
This is also done on other platforms like Amazon Prime. If the streaming services provide works to their customers and there's no valid contract / license, this is strictly illegal. Therefore, streaming services shut down formats from their platform after the expiration of license agreements and when new contracts are negotiated and signed, the formats are then re-provisioned and you can look them up normally. Unless there are no more contracts, the formats will be permanently gone.
As explained so often: Netflix has to pay a lot of money to be able to offer a movie or a series for a certain time. After this time you may be able to resell the movie or series for re-payment or you may opt out of the program.
For Netflix, it is of course very important that they have a varied offer, so subscribers also have something new every now and then. Since after a few months a movie of the most interested in the well-being has been seen, it makes sense, of course, the film then back out and prefer to offer something else so that people do not cancel their subscription because it is always the same gives.
If you take a movie back in the program after some time then that's also part of this variety offer, because after a while there are new subscribers who have not seen the movie yet and are happy if they can see it now.
You also have to take into account that Netflix can't just record everything but has to be content with what the film distributors offer them. That is, the range of possible films is limited by the film providers therefore just come again and again times movies back again that were already there, because Netflix can only fall back on a limited supply of providers
