The pattern I observe is that in old industries, people who paid the cost, try to come up with a big heavy solution (xml, xsd, xpath), but newcomers will not understand the need, and bail onto simpler ideas (json), until they hit the wall and start to invent their own (jsonschema, jquery).
I dunno, I remember the holy trinity of $, % and @ sigils in Perl as my first exposure to JSON-like objects which are the real world's answer to S-Expressions because they address the nameless tuple problem
same goes for java vs php/python