Investment casting and metal injection molding are high-end manufacturing, that can create very strong products if designed correctly. Making gun components (especially small parts) from billets and forgings is almost as much marketing as it is tangible benefits. Most internal parts in an HK pistol are MIM, but few would say that they are low-end, or prone to breakage. Are there limitations? Sure. But knowing where to apply them allows you to create a less costly product that is indistinguishable in critical areas to more costly (and time consuming) techniques.