The chances to hit your target with a hammer is MUCH MUCH lower than a GG shot. Yeah Titans can throw 7 hammer but maybe 3 or 4 hits your target (if you have mastered it) while its almost impossible to miss with a GG shot, it has no travel distance, it is not affected by gravity and easier to aim. And this ladies and gents is why GG can only can 3 or 4 shots while a SB Titans gets 7 (if speced right)