My guess is so there isn't a roar right above the main entrance to the park. Personally, I would love to be welcomed with the roar of a B&M, but others may not.
I'm very excited for this ride and I can't wait to ride it. While I will miss Disaster Transport, Gatekeeper seems to be a vastly better attraction. Hopefully, I will be attending opening day so I can ride it, as I've been waiting for a new roller coaster at CP since 2007!