Vital wheat glutenTypically VWG is used by commercial bakeries to supplement flour protein levels. This especially happens in poor crop years when protein quantity or quality is lacking. Commercial bakers don't want to use VWG because it is expensive ($0.80/lb) compared to flour ($0.15/lb). But some years it is necessary. As pointed out it is also commonly used in whole wheat, etc. to achieve volume, etc. Many countries do not have the higher protein bread flours (11 to 13%) that the US does and they need to supplement with VWG. By the way much VWG comes from Austrailia. Used at low levels as a supplement you really shouldn't taste it at all. VWG does have a higher absorption than flour so additional water will be needed. Or, rather than adding the VWG on top of the formula (with its add. water), subtract the weight of the VWG from the formula flour and leave the water alone. See how the dough feels; you can always add a little more water near the end of mixing if need be.
The low carb craze saw a huge use of VWG not only as supplementing the reduced flour % in formulas but also, since it is mostly protein, as a carb reduction ingredient. The problem was how to deal with all this protein trying to form gluten! Also, using VWG for this purpose was actually cheap since many other proteins and protein isolates cost as much as $3.00/lb. In this case, yes you could taste the VWG.