Problem with less popular formats is that there is no official specs or reliable reference implementations, it tends to break when encoding and decoding with di

Problem with less popular formats is that there is no official specs or reliable reference implementations, it tends to break when encoding and decoding with different OS/languages/libraries/etc. YAML, JSON and XML have very well defined specs and the encoders/parsers have been proven to be very reliable across OS/language/libraries. JSON in special tends to be the least problematic because it is simpler than the others and the browsers implementation is kind of the canonical implementation.