its a tricep and front delt excercise - you dumb fucks
blind leading the blind....
There are several wrong assumptions with your post. It is true that the
flat bench press works the triceps and delts as much as the pecs and that exercises such as pec deck flyes and dumbbell flyes work the pecs more. But it does not matter because the amount of resistence the bench press allows you to put ends up working the pecs more than the other exercises that work the pecs more directly. You put two guys, one of them to perform only pec deck flyes and the other to do only bench press, and the first guy will have bigger pecs after three months, but the second guy will have much bigger pecs after one year. A guy who can bench 400 lbs for reps will have much bigger pecs than a guy who does the entire stack in the pec deck machine for reps.
Also, you can work the pecs far more directly by inclining the bench in a 30 degree angle. This increases the involvement of the pecs in the exercise, decreases the involvement of the triceps and increases the range of motion for the pecs' contractions. The slight incline bench press gives you more and faster growth in your pecs than any exercise that isolates the pecs. The minus is that you get less growth in your triceps and delts. The best exercise for overall torso thickness is not even the bench press, but the flat dumbbell bench press, as this involves even more muscle to balance the weight and works even your back muscles as stabilizers.
SUCKMYMUSCLE
