For all the tools that don’t require different axes of input, there’s less of a need for a gizmo. Inset Faces adjusts a percentage of inset-ness when you drag in the 3D View. What would a gizmo add that’s different from just dragging to set the influence?
There are other tools, such as Shear, where there are axes. You might want to shear along X, Y or Z. Shear then needs a gizmo to do that, consistent with Move or Scale.