My freezer holds prawn shells, salvaged from the fishmonger's, and lobster shells, saved from a meal at a seafood shop. There's even a carcass from the time I served roast chicken for dinner. They will all be used to make stocks for various meals.
Neither do I throw away vegetable peelings: they also go into the stock pot, even onion and garlic skins, ever since I discovered the rich nutrients in them.
Stale bread or leftover toast need not be junked either: They are useful for thickening soups and gravies, absorbing excess salt if you have over-salted a dish and can also be blitzed into breadcrumbs for coating foods before frying. And, of course, leftover wines are always frozen and are added to stir-fries, stocks and gravies. Sometimes, I even add gelatine and voila, I get a wine jelly for dessert.
As for the situation of buying a packet of herbs, like rosemary, for a dish only to have the rest wither away in the vegetable drawer, well, you can place a sprig into your water jug to flavour the water with its fragrance or into your bottle of oil to get rosemary scented olive oil.