Far too many bodybuilders spend too much time exercising the smaller muscle groups such as the biceps at the expense of the larger muscle groups such as the thighs, and then they wonder why it is that they never make gains in overall size and strength.
As your bodybuilding aims become higher, obviously you have to work harder, until, believe it or not, you are performing from 20-30 sets of both biceps and triceps three workouts per week.