Lottery is one of America’s most popular forms of gambling. In 2016, Americans spent $73.5 billion on tickets. They go in clear-eyed about the odds—yes, they’re long—and still spend large sums on what is essentially a game of chance. They have their quote-unquote systems about lucky numbers, and what time of day to buy, and what stores have the best chances of selling them. They’ve learned that if you pick the same numbers for every drawing, you’re more likely to win than if you switch it up. They also know that their money isn’t going to make them rich. But they keep playing, despite the fact that it’s a losing proposition.

It’s easy to see why people persist in their irrational behavior: They have a deep psychological need for hope. The lottery is not just a way to get rich, it’s also an escape valve that allows them to vent some of their fear and frustration about the state of the world and their place in it.

That’s why lottery advertising is so powerful. It’s full of slick visuals and catchy music, designed to create the sense that there’s something out there for you, and all you need to do is get your ticket and try it out. And the odds aren’t as bad as they might seem, because even if you don’t win, there’s a chance you’ll come close.

The first lotteries were probably held in the Low Countries around the 15th century, and advertised with the word “lot,” which may be derived from Middle Dutch loote, or “action of drawing lots.” The winner was given either a lump sum or an annuity that paid out one payment at the start, followed by 29 annual payments that increased each year by 5%.

If the jackpot got big enough, it would be covered by ticket sales and accumulated interest. But the lion’s share of the winnings would be withheld as income taxes. The amount of withholdings varies by jurisdiction, and it can be a significant part of the prize. But the jackpot itself is always smaller than the advertised total, and that’s before considering inflation and the time value of money.

Super-sized jackpots drive ticket sales, and they earn the games a windfall of free publicity on newscasts and websites. But they can also be counterproductive, because the larger the prize becomes, the less likely it is that anyone will actually win.

To increase the odds of winning, jackpots must be lower—and so must the cost of a ticket. But the cost of running a lottery system can’t be lowered to zero, and a percentage of the winnings goes toward paying for workers who design scratch-off games, record live drawings, and help winners. The same is true of video-game makers. No wonder lottery ads are so slick and persuasive, and why you’ll find Powerball tickets in the check-cashing aisle of your local Dollar General.