Because it's a brilliant franchise. Dan Aykroyd is a brilliant actor and writer, whether it be comdeic or dramatic. Bill Murray or no Bill Murray, I still think this film needs to be made immdeiately. To think he wanted out. Besides, all the other old films are having sequels (not just the Disney junk from way back when with trashy sequels). T3 is in the works, Robocop 4 is on its way, Indiana Jones 4 might be a possibility, Star Wars has had many sequels and prequels that it just isn't funny anymore… I could go on. Those are all the reasons I can think of at the moment.