Over the years I have been learning digital sculpting I also learned how to optimize, UV map and paint textures for my models. This is a useful thing to know how to do but it is not strictly necessary if the 3D model is only intended for reference toward Illustration or concept art work because there is the polypaint feature in ZBrush and the vertex paint mode in 3DCoat. Blender also has a vertex paint option although I have not used it myself.
It is not immediately obvious how to show the vertex painted model in Blender because you have to add a color attribute node to the base color for the principled BSDF shader in order for the colors to show in Eevee or Cycles.
This is still rather limited compared to texturing it with the UV map workflow but it could be useful if you just need a render for concept art or Illustration use and want to see how the light and environment could affect the colors of the model.
Even though it is technically possible to rig decimated models with vertex paint, it is still better to have a retopologized model with UV maps because the higher poly model with vertex paint will take a lot longer to render and isn’t really suitable for that use.
As well as this I couldn’t see a way to show the different PBR qualities such as metallic from 3DCoat’s vertex painted models in Blender. In conclusion for a render of polypainted models from ZBrush using Blender this method is useful but if you need something for animation or more complex scenes it is probably better to go through the UV mapping and texture painting stages in the longrun.