Why are cups in movies always empty?

It seems like it wouldn't be hard to fill the cups with something the actors could drink, but for some reason this is rarely the case, to the point where it's very often noticeable. Why is that?

After all, whenever someone sits at a bar, it's not like you'll see someone order a beer and then they receive an empty glass that they pretend is full. So how come this phenomenom only occurs with cups?

I think it is so that they don't ruin takes by accidentally spilling whatever is in the cup. This always perturbs me because it breaks the fourth wall for me every time I notice that the large 44 oz cup is being lifted way too easily.

and beer kegs/barrels are always empty. I move those every day in my job, they're pretty damn heavy!

The problem is the amount of takes and continuity.


If an actor actually drinks from the cup, mug, whatever, they end up doing 15 takes of the scene. They'd be sick.
Continuity is a problem as well. From take to take, the liquid in the cup would change.
Ever seen scenes with food? Most food scenes that have a sandwich or something that is constantly changing size and has different bite marks in it from cut to cut.

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Drives me nuts! Not a film but the tv show NCIS, Gibbs coffee cup!!! If it has to be empty, at least quit setting it down on hard surfaces where we can here the hollow sound and when you pretend to drink from it, at least act as though there is a bit of weight to it!

What I hate is seeing scenes where people are around a table filled with food that looks delicious and costly, and someone makes a dramatic scene, and leaves, and then everyone else pushes away their plates and it's implied that they're now going to throw away all the food.
Maybe wealthy people live like that, I don't know, but it annoys me.

Fill the damn coffee cups with water. Gives it weight and you can drink it.