For quite a few parts, it is easy to import pre-defined geometry as a STEP file. Most CAD systems have systems that allow easily importing libraries of parts in a variety of formats.
Some parts, though, cannot be pre-generated, because they can be customized.
AISC Structure steel shapes are in this category. The profiles are standard, but length is arbitrary, so it is not feasible to simply import a static, pre-defined 3D model.
That's doable, but it is quite a few steps.
Using a parametric tool, you can do it all in one step.
Select the profile, supply a length ( or even an offset face in your existing project), and you're off and running: