We been talking about the reasons you should question the advice of people who spout only one way as "the way." Tonight, I'll hit on one close to home: Lightroom/Aperture vs. any pixel manipulation tools. You may have heard from many photographers who have embraced Lightroom or Aperture that these programs are so good you don't need any pixel manipulation software. You may not need this type of software, but there are some very good reasons you may want to get it.
I use Lightroom nearly every day. When it was still a beta, I became a total fan. I was first drawn to the organizational database, which I used to accomplish with 3x5 cards. I was hooked by its capabilities to search the metadata and apply keywords before I began working in the Develop module. We are big fans of Lightroom and blog about Lightroom capabilities and techniques often.
You might think we would be in the Lightroom Only crowd. Nope. Lightroom is a great tool, but it can't do everything by itself. There are many reasons to add a pixel manipulation tool, like Photoshop, Photoshop Elements, GIMP, etc.
One of the first uses is to add or eliminate things your camera recorded, but you don't want there. Let's say you take a sunrise photo of some antique glassware, in front of a window. You will notice some reflections and dirt that distract from your photo. This is the real photo; I captured it in camera, just like everyone tells you should be your goal.
I don't do windows, even in historic landmarks, so, beware, those distractions will still be there when you go make your photos. I needed to punish some pixels to minimize the distractions. (I didn't get rid of all of the distractions or the photo would look completely unnatural.) You can't do this in Lightroom or Aperture.
To create panoramas, I stitch together multiple photos into one. You can arrange and group them in Lightroom, but, without a way to mess with the pixels, you go no further.
And when you encounter bright sunlight and dark shadows within a single street scene, your camera won't be able to record what your eye sees. High dynamic range photos also require a pixel manipulator. (Yes, this is an HDR, using three bracketed photos.)
There are many more uses for additional tools, but you get the idea. These programs and plug-ins serve a purpose. Limiting yourself to only Lightroom or Aperture can be, well, limiting. Don't let someone convince you that people who use Photoshop are doing something wrong. Only journalists are forbidden from changing pixels in their photographic work. The rest of us get to enjoy all the tools out there.