krillin .... he does nothing

ok he might do a little stuff in dragon ball but in dragon ball z he's completly useless beside the fight with vegeta and he did the spirit bomb( actually he missed and gohan bounced it back to vegeta) but seriously like against cell he started punching him and cell was completly unfased and against super buu he just missed why was he in dragon ball z and in gt it just doesnt make sense i know he is a main character but really they would be the same without him so why is he in