I'm programming a drawing plugin for autocad to draw cross-section in beams and ribs. I need to know if it is worth it to add (to my plugin) the feature to add more than two rebar rows, or if I'll be covering the most use cases with two.
Depends on the context.
Standard residential and office buildings usually don't require much rebar, so two layers should be sufficient.
Structures under greater loads (i.e. bridges), however, can often have more than two rows. This can obviously include residential/office buildings with more unusual architecture requiring wide spans between columns, etc.
Given that, I'll leave it for you to determine whether designing for only two rows will satisfy the needs for your project.