That doesn't make sense. If that was the only reason, it would be easier and safer to just get people to take their liquid, in its container, out of the bag at scanning time

Why can't the liquid be allowed on the plane after the rest of your luggage is scanned then?

I thought that somebody could sneak a explosive liquid into a plane via cup or bottle, and that the liquid could look so much like coffee or water or fuckin diet Pepsi that the security people were like "nah bro we aren't gonna test it".