>>1011603
You can use blocks as a quick and dirty way of copying geometry from edges converted from a ref model to another model without having to use external references. Example being a pcb hole pattern from an imported connector model, or a standard panel cut.
A other one is layout sketches. A pcb related example is placing boards in a product. Use blocks in sketches and mate pcb assemblies to block sketch elements. Easier and quicker to drag blocks in sketches than faff with mates...