Every big movie and franchise will usually come out with a sequel if it became relevant enough. It did so well the first time, why not the second? But, usually, these sequels are very lowly rated among critics and do not make nearly as much money as the original. There are a lot of reasons that this does happen.
One of the major exceptions to this rule are sequels that were planned from the beginning. This is because a already established arc was planned, making it not seem like a remnant of what it once was but, a well-done continuation. However, this doesn’t work out too well when the movie was originally planned to be just one movie. This is because when an arc is already established and finished, it is extremely hard to continue something that is already wrapped up. This usually leaves the sequel to not have to same tone and emotion and makes the writing less than subpar. It also usually leaves the watcher wondering why we needed this in the first place.
Another huge reason is that the same creative team is usually not available, making it very hard to match the standards set by the original. One big example of this is “Mean Girl 2” (yes, it exists). Because Tina Fey was not apart of the writing team, it left it feeling like a Disney Channel movie instead of a PG-13 comedy. Which is why you probably didn’t even know it existed.
Making these pointless, cash-grab movies just because they know fans of the original will go see it just makes people disappointed and lose interest in the story and characters. They cause something that people use to enjoy to be dampered by the unnecessary continuations.