I asked myself the same question when I got out of school. All my portfolio stuff was created in Photoshop or Freehand. However, once I got into the real world and got a job as a pre-pressman, I quickly discovered the necessity of a page-layout application. For large amounts of text, multiple pages, complex grid systems, and just setting up multiple instances of an image (business card, for instance) accurately and by the numbers, is imperative. I was dubious of a dedicated page layout application at first, but I quickly began to appreciate its features.

As has been echoed on this thread, by all means, get InDesign, or at least PageMaker. But *some* page layout application. I personally have CS Premium. I highly recommend it.