[kolapuriya]

Depends on what you mean by "parse". If all you want is to search a document that is known to be well-formed, find an element that meets a few criteria, and grab a value out of that element, you can sometimes get away with using regex to find a substring that "looks right" without actually parsing the document. Running your document through an actual parser gives you access to more information about the structure of the document and the context of the elements of interest. Actually parsing your input is therefore more robust to unexpected variations than any of the superficially-cheaper alternatives that people try.