Several reasons:
Times are hard, persons want or at least are trying to get some "cash for their trash".
The Internet has not only allowed clubs such as this to grow, persons doing research not know there is a "market" for things they would have chucked to the curb otherwise.
Then there is the growing number of persons seeking out (and maybe paying too much for) anything metal for scrap. IIRC, there is even a few new shows on cable about it.
Finally, considering the cost of a new washing machine, and what one is getting in that area, an "old" washer in good condition even at inflated prices,will out last the former.
Just my two pence. Do with it what you will.
L.