Because if liquids were really a threat, all you have to do is send 5 guys through security instead of 1, and then combine their liquids on the other side.

Also for the reasons outlined here:

http://www.guardian.co.uk/science/20...rport-security

Schneier makes some very good points in his article. If you try to bring a gun or hand grenade on a plane, and you're detected, the contraband will be confiscated and you'll be arrested. This is because these items are considered a potential threat.

However, if you try to bring a jar of spaghetti sauce on board, and you're detected, the contraband will be confiscated. This is because spaghetti sauce is considered a potential threat. However you won't be arrested - The sauce will be thrown away and you'll be sent on your way.

Why not? Apparently the gun and the spaghetti sauce are both threats - Why is the accused perp treated differently with these two threatening items?

Because you're not arrested with spaghetti sauce, if you're a terrorist you can keep trying over and over again until you get through with your jar of sauce, because there's no consquences to your action, unlike with a gun.