Yes, it is unlikely if we take only one week, but take 30 weeks, and it is not that unlikely anymore, right? I know that each week is independent from all the previous weeks, the wheel has no memory of other spins and stuff, but here's the thing: although the current US Powerball has 292,201,338 possible combinations, and thus it is very unlikely for the holder of just one ticket to win the Jackpot, all the holders together somehow manage to win it once in a while. In fact, since Powerball launched 30 years ago, 393 tickets have won Jackpots. In short, what's unlikely from the first try is not that unlikely with many tries.