A few years ago the government changed the rules so that children in foster care (ie some of the most vulnerable, trauma-experienced, emotionally damaged children in the country...you get the picture) could stay in care until age 21. Those living in childrens' homes, however, (sometimes even more vulnerable and damaged hence why there are no foster places found for them) still have to leave age 18. Some have been found sleeping rough. These are kids whose lives have been made hard due to the actions of familiar adults they trusted. They are often not emotionally competent to look after themselves aged 18.
Here is a petition asking to change this situation and I hope you don't mind me sharing it:
you.38degrees.org.uk/petitions/equality-of-leaving-age-for-all-children-in-care?bucket&source=facebook-share-button&time=1518679443
