I knew someone in the restaurant business in a similar situation. Mostly cash. Inside job from disgruntled employee, got more than 100k from him.
Many small business owners, especially from southeast asia, simply don't trust banks. Some are not citizens and have no credit history, others (like in the example above) can not use banks as the income is not reported to the IRS. So there are many reasons why a home may have a large amount of cash, jewelry, etc. These are not rich people, just people that have circumstances which do not allow them to utilize traditional saving methods.