Because Tide is universally popular in the US, amazingly so. You could go into a CVS or Walgreens in the US and 70%+ of the detergent on sale will be Tide branded.
Since people are always going to wash clothes, retailers can guarantee they'll shift, and it's virtually un-perishable - and because the margins on tide are rather low, shops will happily buy suspect goods: they're practically untraceable and will shift fast.
Practically everyone does laundry, but not everyone drinks coffee. And those who do drink coffee will have differing tastes and far more varying brand loyalty than the detergent market.
If you think a bit, you really can't come up with anything better. Gourmet coffee is a bad currency because it's very local and few people actually need it.
EDIT: And if it's already ground when you buy it, it's no good, by the way. ;)
I used to work retail. Well, during Bush the 1st. Anyway there are multiple markets. Its not like on the internet where there's pretty much ebay and nothing else. Locality and physicality breeds multiple markets.
One is a kid can probably walk out of his parents basement with a bottle of tide and mom and dad probably won't notice quite as obviously as if the kid walked off with a $20 bill. So at least some Tide is from unemployed teens smoking up via mom's walmart bill. Obviously not terribly high volume, but...
Another is there is already a booming market in turning high value food stamp food into money for "whatever". Our food store was surrounded by bars where a cold steak presented at the bar resulted in maybe half price in cash being returned, more or less. Also you can buy a steak OTC, cooked even, from the bar, for cheaper than we sold them. Whatever drug market operating in steaks is parallel or in competition with the existing food stamp market in steaks. This also explains the anecdote WRT food stamp corruption the crooks are always buying stacks of steaks with food stamps... they're the universal currency, not doritos or rice bags or whatever. If you're trying to turn stamps into cash you buy steaks. (yes I'm old, and I'm well aware its a debit card like scheme now, but nothing really changes with the market)
Because it is ubiquitous, there is constant demand for it, a consistently high retail price, and there are plenty of retailers willing to fence it in large quantities.
Interestingly, it would also be rather easy to counterfeit, assuming the fragrance isn't impossible to nail down. Wonder how long before we see that start happening...
