The answers on this thread are very interesting, and give a lot of insight into why different socioeconomic groups gave children who do differently.
For working class families, it seems once a child is 18 they should pay for everything themselves. No help, so if they have a car they better get a job and pay for it. Even if parents can afford to help: no, the young person needs to learn the harsh lessons of survival.
For middle and upper-middle classes, parents see it as a privilege to help their child establish themselves in the world. Your child will be competing as adults with others of similar ago whose families will buy them private tutors, apartments, cars, access to prized internships, and every other advantage that will help their adult life be successful. If a 19 or 20 year old is working like a donkey to pay for car insurance, then their focus on learning the sorts of skills to thrive in this world is reduced. These families actively support their children into their twenties, and as a result their kids thrive.
Do you think that the families of Prince William and Harry’s school friends made their children pay for their own car insurance at 19? No, they do everything they can to give their child every advantage they can.
No doubt it’s unfair. But a good part of the outcomes of each group is related to the cultural practices of the group. And withdrawing parental support from a 19 year old for something like car insurance, when side of their luckier peers will have cars AND flats bought for them at that age, does make us reflect on how to best help young people