Pretty much a “to the point” question right? Let me ask you something. And this goes to all technical inclined people. Would you want to hard code HTML in order to create a website? Or use something that would make it easier for you to make one, like a WYSIWYG editor?
The answer is obviously the second choice. And with regards to XML, I would also prefer to use a tool that can easily help me create XML documents and save me time. Time is gold and if you save a lot of time, you get to save a lot of other things like resources.
There are many things that one encounters with regards to XML. There are DTDs, Relax NG schemas, schematron schemas, XML schemas and even XSLT stylesheets. Even I used to want to hard code everything since I could learn and understand the logic of a technology better but using a tool that can help me finish my work faster? No brainer. An XML editor is a very helpful tool.
XML editors these days include great features that make is easy for developers to do their work like syntax coloring, XML folding to simplify working with huge documents, XLST transformation where you can run this feature in just one key press or a mouse click as well as intelligent XML formatting to make your XML documents easily readable.
XML is a brilliant technology. It avoided the limitation that HTML gave to users where they are stuck with a fixed set of tags. With XML, users can structure their data in any way they want. An XML Editor is the perfect compliment to working effectively with XML.
Believe me, this comes from experience. If you have not used an editor, then try it and see just how much time can save you in working with them.