There is no legal requirement in the US to have a picture ID card, either. Unless you want to drive. Or, in an increasing number of states, vote. Or get on a plane without a ton of hassle. Or... well, you get the idea.
It is possible for something to be "not legally required" but still have a very high degree of adoption due to the inconvenience caused by not having it.
It is possible for something to be "not legally required" but still have a very high degree of adoption due to the inconvenience caused by not having it.