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On an emotional level, XML is annoying.

XML is strict and unforgiving - great for validation, tools, and stuffing into SOAP envelopes. OTOH, for all of HTML's warts, it is flexible and forgiving to humans. Great developers and designers want to be happy working with their creations, and WYSIWYG tools often do not fit the process. So when you are forced to work with markup by hand, the perceived friendliness and ease of the markup language is significant.

In the end, to each their own. But programming languages are a popularity contest. Especially new ones.