correct me if Im wrong but the the faster you reel the deeper it goes correct? so I dont understand not using a faster reel?
Not necessarily. It might achieve maximum depth a little quicker. But if you got too fast some baits will blowout or roll over. Think of the gear ratio as if you were pulling your boat. Would you rather pull your boat with a sports car or a truck? It's more about the torque. The lower gear ratio reels can crank the bigger deep diving crankbaits with less effort.
You are better off getting a properly designed rod that allows you to make farther casts. The longer the cast you can make helps you achieve deeper depths along with line size. The smaller the line the less diameter thus less drag. You will get deeper with 10# or 12# line than with 17# or 20# for example.
In the end it's all about preference and what you have confidence in.