Comment by sqrt17

That seems like the difference between object-based (early VB) and object-oriented.

XSLT is referentially transparent (no setf for you) but withholds from you most of the goodies that people take for granted in functional or logic programming.

You could see it was written by well-intentioned FP enthusiasts. IMO the best alternative at the time when XSLT was developed would have been XMLPerl - embedding an imperative language in something that deals with the XML-specific parts appropriately. But Perl was never enterprisey enough, and XmlPerl died a painless death.