The casino is not in the business of selling its chips as a retail business. If you went into a clothing store and wanted to buy their display case for your home, do you think they would sell it, even at a profit? The casino, as you say, is in the business of making money off their games... a lot of money. They don't particularly want to spend the time to keep reordering the tools of their trade.

Chips made to be collected are another story, and in my opinion are looked at by the casino primarily as an marketing tool, not a profitable sideline.