Here's the problem with that perspective....
Some f/as (and pilots) "create" trash. They open unused bottles of wine at the end of the flight, and pour a little out of them, so they can use the argument, "Well, it was just going to be thrown out." If it is returned to the caterer unopened, AA gets credit for it, and it reduces our overall catering costs.
We are told, you can consume any leftover, unused meals on the the aircraft. You can not take anything off the a/c. We are even allowed to eat unsold fresh sandwiches on the longer flights, but we can not take an unopened sandwich off the airplane.
If you start making exceptions, people find a way to make sure what they are stealing falls into the exceptions category. In the long run though, it doesn't matter whether or not the rule is petty, it is the rule. As they used to say at my former employer, "the Golden Rule in business is He who has the gold makes the rules."
Exactly. Ya tell employees that they can take the stuff that's destined for the trash and some of them will find a way to get what they want into that "going to be thrown away anyway" category. Only way to minize that is to prohibit taking the trash before it's actually in the dumpster. That doesn't eliminate it entirely, but it takes a very determined thief to dig thru the dumpster for their treasure.