Oh god I hadn't considered that aspect of it! My parents had a trust fund thingy set up for me and my sister that automatically came to us when we were 18 but it didn't occur to either of us to fritter it away or blow it on drugs/alcohol-we spent it on university. I was just assuming dd would be as sensible as me (!) but if she is anything like her father then she would just waste it-eek!
I do think it was partly the relationship we had with money growing up-eg my parents didn't have a huge amount, we had to earn our pocket money, buy our own clothes etc out of it (apart from school uniform)once we hit our teens so we learnt to budget quite early on. We also paid our own way through uni(with student loans). DH on the other hand came from a wealthy family who just handed over money whenever he asked, if he blew it there was always more and his money was just for fun as rent, food etc were all paid for. He has only learnt in the last 2 years that it isn't limitless and that he needs to be more responsible with it.
But, as some of you have pointed out, that isn't the only thing that determines it and no matter how much we teach the dc about the value of money they will still be their own person and who knows what their priorities will be age 18.
Eek!