Actors who join shows or movies without liking the script

Twice in a few weeks I’ve seen stories about joining projects they have deemed beneath them despite having read the script.

We have the Ed Harris example. Then last night I was reading something about Rutger Hauer, who read a script, called it vile and pornographic and not to his liking, but joined the movie anyway under the impression they would rewrite the movie to do more for him.

What am I missing here. Why on earth are actors joining films when they actually have read the script and still don’t like the project