Canon is number 1 and Nikon is number 2 and nothing else is very close in the DSLR world, so you're going to see most images taken with one of those cameras. Both of these companies offer a large selection of excellent equipment that is used by amateurs and pros. They are not the only camera manufacturers, but they are the 2 most popular, probably because they do manufacture top of the line equipment that can cost thousands of dollars. The availabililty of such equipment allows users to have an upgrade path if they decide they want to pursue photography seriously or as something more than a hobby.
If your Pentax meets your demands, then I'd say you bought the right camera for you. Pentax also has lenses that cost over a thousand dollars just like the other manufacturers, but if you find no need for them, what difference does it make? As long as you're happy with your equipment, what difference does it make what your equipment cost, the brand or what other people use? I don't think any of us got into this hobby to see how much money we could spend. I have quite a bit of equipment that I've bought over a number of years (quite a bit was bought used). I've also bought and sold lenses as my shooting style changed and I tried to find what worked best for me. I'm currently happy with my equipment although my camera is getting rather dated and could use an upgrade, but I'm not in any hurry. It's capabilities still far exceed my skill.
Les, I don't think anyone on this board cares about what equipment the other person used to capture an image. Some of us jokingly post envious remarks about someone's new equipment, but I'm sure each of us is actually happy for that person. IMHO, owning better equipment will not make you a better photographer, but it may allow you to capture better images. If those images were captured by a Nikon, Canon, Pentax, etc., what difference does it make? If the camera and lens cost hundreds or thousands, who cares? If the image is technically perfect and the post processing is superb, great, but the real question is was the person that took it happy with the results, if so, what else actually matters? If you're happy with your equipment and the results you obtain, what more could you ask for?