1. Ease. Who likes doing dishes? I don't. You can normally make an entire slow cooker recipe using only a cutting board, knife, peeler and the slow cooker. If you find frozen or canned veggies, you can cut that down to one dish--the slow cooker!
2. Healthy. Unlike most traditional recipes, slow cooker recipes don't call for added oil or fat since they use water and time to cook. No fried foods here!
3. Cost. On average, a slow cooker will cost between $30-$100, and generally last forever. My mom still uses the slow cooker she got for a wedding gift I won't tell you how many years ago. Don't tell anybody, but you can use less expensive cuts of meat, and because of the slow cooking process nobody will ever know!
4. Time. The slow cooker is the only kitchen device that allows you to cook while across town. It's as simple as adding your ingredients, turning it on, and going to work. Or going to sleep. Or going outside to play with the kids. Wouldn't you rather do that than spending your day in the kitchen?