The problem with lotteries is that many of the players aren't like your dad. There are some serious ethical questions that arise when you think of lotteries are guaranteed to lose the vast majority of players a substantial amount of money:
1) If the state didn't run the lottery, who would? Would that money get funneled into public works if the state didn't run the lottery?
2) Is it ethical to market the lottery in order to create new players?
3) When the lottery is marketed (as it heavily is in many states), is it targeting vulnerable groups, like the poor?
4) Is playing the lottery an expression of hopelessness for some people? They know that their $5 is never going to multiply to $10 (the way it might for a wealthier person), so it's easier to risk that $5 for a chance to win $5 million.