Has somebody been watching Gilmore Girls recently?

Heee -- yes, I did watch GG, including even the series finale! I want to be Lorelei, and I want my monster foster kids to be Rory and Lane (I'm not, they're not, sigh). But I've noticed it on other shows, too ...

A couple of practical reasons, I'd guess. (Coincedentally, I just a couple of weeks ago I was shooting a scene for a friend's short film in which a couple of the characters had to "drink" out of -- yes, empty! -- to-go cups.)

Scenes usually require take after take after take, and final scenes are edited together from bits and pieces of various takes. So there would be a continuity issue -- a character sips out of the (fullish) cup in one shot, then in the next shot is tipping back the (half empty cup) in the next shot, then is back to sipping out of the (fullish) cup in another shot. Continuity is enough of a nightmare to maintain (does he have the pen in his hand or pocket? Is the salt shaker on the left side of the cup, or the right? Is her hair tucked behind her ear or loose?) without adding one more factor to the mix.

Also, if you did try to keep the cups filled, it also means you've got to have some sort of liquid on set or (even more of a pain in the ass) on location, so that you can to keep filling up the actors' cups as they drink. Which also means that you'd be making it more likely that the actors will have to pee sooner than they might otherwise.

Of course, IANAPropmaster, though my roommate is... I can ask her when she gets in!

I shall market weighted yet empty faux to-go cups and become rich RICH!!!

Speaking of props, I couldn't believe how absolutely fake some look in real life, Star Trek's especially.

Claudia, your weighted cups would do wonders for community theater. That's one of my biggest pet peeves when I do a show - the stage manager/director is so worried about ruining a set piece that someone has loaned the company that all the teapots, coffee pots, drink glasses, etc., are all empty and the actions of pouring and drinking are pantomimed. So aggravating! Fill the damned things with water if you have to! It's very obvious to the audience if you're tipping back an enormous cup or goblet with no difficulty that there's nothing inside it.

Yeah, clearly they're going with the to-go cups in the first place because it eliminates continuity problems.

Also, real stuff to drink on set means pee breaks, and the ever-present potential of a costume disaster.

But you could add something to the to-go cups -- a lump of clay or something that would make the carrying look real without adding liquid.

Sigh, I need to move my brain on to something more important.

Yeah, and why don't they put something in all those "heavy" suitcases and boxes, instead of relying on the actors to have pantomime skills?

And you can get lenses for glasses that do nothing, but still aren't completely flat, too.

Speaking of props, I couldn't believe how absolutely fake some look in real life, Star Trek's especially.

Yea, I saw some of the props for Classic Star Trek once, phasers and tricorders, and they looked like they'd been carved out of chunks of 2x4 and painted with house paint.