I'm guessing because the lottery system needed to generate a large number of random numbers (given that they are running lots of lottery systems), and this give

I'm guessing because the lottery system needed to generate a large number of random numbers (given that they are running lots of lottery systems), and this gives a fairly verifiable way of doing that from one initial chunk of randomness. That said, I don't work in this area, so you should give my comment very little weight. :)