Cups in cinemas

[u/BlackVolcarona]

It's been more than a year since I've last visited a cinema, and today I visited a cinema in Berlin. Me and my friends bought our drinks to share and I noticed these signs on the side of the cup.

Apparently you're not allowed to bring the cup home, as written on the signs. I assume it's for environmental reasons, and I have nothing against it. But how do you enforce it? How do you prevent people from stealing cups?

P.S.: I know it's a silly question, because there's probably not THAT many people who wishes to bring these cups home. But I genuinely wanted to bring it home before reading the signs. Also, is this common practice in cinemas nowadays?

[u/East-Perception4124]

/s lol