The other end is anchored somewhere, likely to the frame. This doubles the pulling power of the winch, like using a snatch block. It doesn't leave you with much reach though, especially with a short-drum winch. Maybe it does have a specific work application just behind the truck, like pulling something up onto a trailer...
Interesting find--I've never seen it done that way before.
Just guessing, but I think the sticker above the winch probably refers to it's max load of 500kg. (1100 lbs) That looks about right for the size of the winch and it's line. More fascinating is the truck itself. I did a google image search and found that the Hilux is a 1990 4 door with only 42,000 miles on it. It's for sale for $10.900. The downside is that it is in Japan. The truck also does not appear to have a hitch, so I'm not sure about the theory that the winch was used to put stuff on a trailer. http://www.tradecarview.com/used_car/japan%20car/toyota/hilux/11837713/photo/?sid=300&pn=3
Just guessing, but I think the sticker above the winch probably refers to it's max load of 500kg. (1100 lbs)...