Rigs are often compared to Lego systems, since they can be assembled according to your imagination. It's hard to justify the cost of industry standard 15mm rigs if all you need it for is to stabilize your camera. You can already do this with a few broomsticks and duct tape.
It starts to make more sense once you start to involve mounting audio accessories, lighting accessories, monitors, evf solutions, follow focuses, and matte boxes. Especially since some of those items require rails to mount. Clamps and rods also make it easy to redesign and customize size and shape depending on the individual. You can grow with a starter set of rails, or you can shrink down from a large rig. Not to mention the benefits to traveling. A large set of rods and clamps can be packed up pretty nicely. Lastly, there are many who just want the pure aesthetics of it.
Here's the direct links to the products if you have a Canon T3i with Battery grip and looking to rock the Letus Hawk VF too. If you have questions, you can always contact the support team @ LetusDirect.com