As an a detrimental character in the franchise, and the work that Neve Campbell has put in to give us the Sidney we know and love…. We want her in the film and think that she is owed due compensation for what she “personally” has given to the franchise as well as how popularly powerful her character is to the Franchise’s audience. 
To quote Neve: 

“Sadly I won’t be making the next Scream film,” stated Campbell. “As a woman, I have had to work extremely hard in my career to establish my value, especially when it comes to Scream. I felt the offer that was presented to me did not equate to the value I have brought to the franchise. It’s been a very difficult decision to move on. To all my Scream fans, I love you. You’ve always been so incredibly supportive to me. I’m forever grateful to you and to what this franchise has given me over the past 25 years.”