Software has gotten so complicated that most people simply dont have the time in their entire career to learn everything,
so they pick what they want to learn, what their boss tells them to learn and for the rest pick what seems easiest - and if it works you stop there. And for a lot of people that is not bad or wrong. The universe of programmers is not what it was 30 years ago. There is a huge amount of jobs for people to "just" put together pre-built parts. Expecting everyone to be an expert at everything is unrealistic.
And face it, you *do* have to know XML quite well to use the "simple" tools ... and when to choose them over more complex tools.
When do you pick DOM or SAX or StAX or XSLT or XQuery or xmlsh or XPath or XProc ? To actually make a useful decision on this you actually have to learn ALL of them