One of the things that SSRI did with their excess cash was to buy Silver when the price was low. They more than doubled their investment and it also helped their share price. Rather than sitting on cash they were sitting on the next best thing, actually better than cash. Miners dont do it because they figure they hold enough of it. But on the other hand if they have the means and they can get hold of products they sell for less than it cost them to produce it then why not?
Not only are they supporting themselves but they are also generating a market for the products.