they raised it to 21 because people were being forced into marriage, look at the doc who was 33yrs old in the news recently who was held hostage be her parents, after being tricked into going to Bangladesh for an arranged marriage.
i watched a tv program i think it was filmed in India, where the British embassy had a help line, where they would go and visit with police, British citizens who were being forced into arranged marriages by their parents and try to free then , and get them back to the uk. those who worked at the british embassy went out of their way to help and free them, so for once ato the embassy..