 You think you'll spend less money in retirement. Certain expenses are associated with working. That will stop once you retire, such as commuting expense, work, wardrobe, lunches, so on and so on. But you'll also have a lot of free time, and that can be a temptation to spend, making retirement budgets so that you know that you can need and have and save what you need to stick to it once you've retired. Hey, guys, why would you spend less money once you've retired?