It's 6 months, after passing their test, that's being recommended. Not all the way up until they are 21 (unless of courses they pass their test 6 months before turning 21). If that demotivates them from wanting to drive, then they don't really want to drive. They want a status symbol for their mates instead. People get on without cars all the time, they can get on without the need of passengers for 6 months also. https://www.bbc.co.uk/news/articles/cvgl5jvz0dqo