You could, but I think it's very helpful to have the money in a separate account so you're not as tempted to spend it (or get confused about how much of the balance is for what). When it's in a general savings account that's earmarked for a specific purpose, you know it's off-limits unless it's for that purpose. Besides, you're not earning any interest in a regular savings account. Trust me; it adds up fast; more on this in the question below.