There is a lot of hypocrisy on this matter. If it’s wrong to leave a 14 year-old alone in the house, surely it would also be wrong to let them go out on their own! Nobody makes a fuss about children being allowed out unsupervised unltil they end up drunk in a park at 2 a.m.!
A childcare professional acquaintance once told me that, strictly, nobody under 14 could be left alone at all in a house. I reckon this, if true, dates from the times when most houses had open fires and the obvious fire risks were greater.