Your local picture framer is sinking in off-cuts. They are sinking in molding. Space is a premium to the framer. They have to manage their stock in the space they have.
If the framer is blessed with a large warehouse to keep old lengths of moldings then they are in no mood to let you have off-cut mountcard or frames made in old lengths at a reduced price.
If you find a picture framer that has a small workshop you have struck gold. They want to get rid of stuff and if you offer them something for it, it will be yours.
Old moldings, especially the wooden ones, bleach in changing light conditions and are rendered worthless after a few years. If you are an artist an looking to frame your artworks cheaply, you could easily offer something for the old bleached moldings and have them limed.
Remember you framer is a genial person and you don’t need to get into an arm wrestling competition to convince them of the benefit of liberating space in their workshop.