It got popular because it's far easier to read and edit hierarchical and array data in YAML than it is in XML (or JSON).
Most of the time I don't need a format with support for some esoteric charset or namespaces or any of the other baggage that comes with XML, I just need a quick way to exchange regular, structured information, possibly with comments, in UTF-8, that is easy to read and write.
Show me a better format that doesn't make my eyes bleed from the angle brackets (or the curly braces from JSON) that is commonly supported across lots of programming environments and I'll happily switch to it.
Most of the time I don't need a format with support for some esoteric charset or namespaces or any of the other baggage that comes with XML, I just need a quick way to exchange regular, structured information, possibly with comments, in UTF-8, that is easy to read and write.
Show me a better format that doesn't make my eyes bleed from the angle brackets (or the curly braces from JSON) that is commonly supported across lots of programming environments and I'll happily switch to it.