I completely understand your frustration. There was just a Dr. Phil show on this very subject and it is very definately a growing trend. In this case it was their daughter who refused to move out. She had graduated from college and had a good job but in spite of her parents giving her deadlines to find a place of her own, she wouldn't budge. She came right out and said what you said. She didn't want to leave her comfort zone. Until she could afford to live like she was now, she wasn't going to leave. She was doing nothing to save toward that end. There is a complete disconnect from reality with alot of young adults today.
Dr. Phil gave the same advice that Miss Cellane gave. Until it's no longer fun to live at home, they'll never leave. If I were you I'd stop making meals for them. They have jobs and there are restaurants. Come up with a time line and stick with it. In the Dr. Phil case it was 8 months. And during that time frame do whatever you can to push them out of the nest. If their on your family phone plan, take them off. If they don't pay towards cable service, take the tv out of their room. It's not mean. It's for their own good.
FYI, I kicked my DD out when she was 19 and it was the hardest thing I ever had to do. In my case it was because she refused to abide by any rules and was headed for serious trouble. I was unwittingly facilitating it in the guise of love. She told be a few years ago it was the best thing I ever did for her. She was forced to grow up because life became about how to find the next meal, not where to find the next drug dealer. That's not your situation exactly, but it's the same dynamic. Nothing will change until something changes.