When this is the right tool
Most PDF advice assumes you already have a document. Often you do not — you have text in a chat window, an email, a notes app or a terminal, and what you need is a file you can attach or print. Making a Word document purely so you can export it is two steps more than the job requires.
It is also the quickest way to get a clean copy of something formatted elsewhere. Paste an article, a set of notes or a table from a web page and the structure survives while the page's styling is left behind.