Well, of course they do it to save money. But consider a fairly close analogy: if they are selling alcoholic beverages which are as comparatively contaminated and devoid of alcohol as these tests show, would they get away with it? Of course not. Why? Because people would notice. Why? Because, for its intended purpose, alcohol very clearly works.
And I'm not saying *no* supplements work, I take several regularly myself (including turmeric, though I don't buy it as a supplement). But the point remains, if they are knowingly putting some random organic detritus in a capsule and calling it ginseng and taking the risk of getting caught doing so, they are making a rather hefty wager on the belief that consumers won't know the difference.