To be honest the distance the weight moves in a squat is at least twice distance weight is moved during a flat bench press. Also, in a squat there is no pad to lay on to balance your body. Squats require much more balance than any bench press.
You are comparing two different things here 1) a completely free weight exercise like squat and 2) a partial free weight movement in which the body is stabilized from head to ass. Therefore, since squat require a person to move the weight farther AND require more balance, the weight used on bench press should probably be more or equal to your squatting weight.
Using the "logic" of this thread a bigger muscle should be a stronger muscle. If you say, "Hey the legs are contain much more muscle mass so therefore, the weight used on squats should be greater than the weight used on bench press." Then, using your logic, the back muscles (which are much, much larger than the pectorals) should be stronger than the chest. How many of you 315 lb bench pressers use the same on rows? How often do you make of fun guys who bench 495 but are never seen rowing even 315??
