Generally, management has decided that the time and money required for inventory management outweighs the value of catered goods.
Add to that that what's left behind of the consumables will go to the cleaners; so, management generally tolerates crews helping themselves to whatever would otherwise be binned.
As has been noticed, there are always a few who abuse the situation.
With the technology available these days, I would barcode every valued item such as wine and miniatures and complete cases of packaged items. At end of flight, the crew would be allowed to check out controlled items on offer at concessionary prices. Anybody found in posession of controlled items without a machine generated invoice would be subject to termination.