Re: Is this just an English thing ?
The older you get in Germany, the more you get away with "du". This is because of the commonly accepted code that between two persons the older initiates the switch from "sie" to "du". Basically it is like this: Small children can say "du" to anybody, around 1st or 2nd grade at school they should use "sie" when addressing grown-ups which are not family. Usually from the 11th grade on teachers start also to use "sie" when addressing the pupils and from 18 on there is always "sie" in both direction for strangers. The older person can always implicitly or explicitly propose the "du". The implicit version (just start using "du") can be awkward to the younger person, because it stays a bit unclear if the reverse "du" is really OK. In certain situations it is also OK to refuse the offer of "du", but it can be taken as rejection of friendship in other situations.
Quite complicated, but I personally like it like this, because it helps to keep a kind of distance to people you do not want to have too close to yourself.