A friend has two kids who have left school now. One has gone to uni and has a student loan, which he is using to rent a room, do his own shopping, cooking etc. he is becoming independent, and appreciates how much food costs, and cooks for himself. The other one is continuing in FE with no student loan, living at home. He always takes the easiest option out of the fridge, rarely cooking, and if he has £10 to do some food shopping, he goes the takeaway.
I will let you know in a few years time whether or not either of these young people are fully independent, but I know which one I rate the chances of.
Making young adults aware of the cost of living is a crucial part of their education, failing to ensure that they find out one way or another can lead to problems later as plenty of pp have pointed out.