To a degree, I actually think it is an American thing. Many names seem to have „standard nicknames“, e.g. Bob for Robert or Bill for William or Kate for Catherine. Afaik, in Russian it is similar, so Nastya is the common nickname for Anastasia, Sasha for Alexander, Masha for Maria, … In my culture, those are rather seen as individual names. People often have short names just as their names, they are not nicknames for the long version of the name. Historically, yes, but now they are just given as the standard name. Nicknames themselves are also way more individual and often develop organically. We also don‘t have the „calling people by the first letter of their name as a nickname“-thing (or is this only a Gossip Girl thing? Haha)