While there were specialized uses for the dagger, it tended to be viewed as a thrown weapon or something an assasin would use. An example of the specialized uses were the ermei piercers and ring daggers. Both were designed for use in water with variations mainly focused on being able to swim and still have control of the weapon. Recon is the obvious reason but I wasn't there so I can't verify this information in a non-vague manner.
Some other uses which came to light recently was for the use of a knife in urban settings. While it should have been obvious to me, there are places that you can't take a sword. The Dagger was specialized for killing and made a perfect weapon to carry into small spaces. When people carried knives to eat with, a household could not garantee the safty of all the guests. The host began to provide utensils so people would not have a reason to pull their own knife. The dagger design became more popular shortly after this new custom became popular. It also has impressive applications in a close quarter combat role. The survival/hunting knives are still better but the dagger is easier to fabricate and cheeper to maintain.