It’s because the big studios don’t want to take a risk on something new and original, they almost always want to go for the “safe” bet and pick a sequel, spinoff or remake of an established IP that they know will make money. All they care about is profit. Making flims as an art form is is a struggle for passionate directors. Take Guillermo del Toro for example, he said recently (and I’m paraphrasing) that he still gets a lot of push back from studios when he’s trying to get his projects of the ground. That’s because he’s an artist and art is a risk.