[justin66]

It is true that it requires effort for the developers of a software program to support a given file format. Beyond that I'm not sure what your point is.

[galangalalgol]

Not the op, but one point would be, why did we even pick xml, when we had latex and html? Why is a relational database the right tool for a document format?

[cxr]

They're constrained by different requirements. The comment was clear enough:

"those are completely different uses"

It's not a hard concept to grasp. There is no riddle to decipher.