PreCheck is not a right. It's a program you pay to participate in. GE lets you participate in the program without any additional money or action beyond entering your KTN and info properly. Most of us get PreCheck regularly but it's not a 100% situation no matter how you enroll.
The best deal is Nexus if you qualify and can get to a Nexus enrollment center.
GE is next best followed by paying TSA for PreCheck.