It is always said to be for the farmers, but they get up when the cockerel crows. I suspect the farmers are just used as a scapegoat. After all, the cows don't go "Wait a minute, clocks went back. Hold off on the milk for an hour ladies!".
Now it appears to be to reduce casualties in Scottish children walking to school. Didn't they find that more people get run over when we don't change the clocks back to GMT? And in summer, it is light for nearly 18 hours a day, without BST it would get light at 3am!
I am really not bothered about clocks changing, I have never been caught out.