It’s kind of a short-cut/fix to not having the best quality flour. Usually good Pizza flour should have a high protein percentage (I’ve heard values in the 13-15% range), but that’s really hard to find. My Pizza flour has 12%, my general purpose flour has 10%.
Vital Wheat Gluten is just the purified Protein from flour. It’s 80% Protein, so I add a bit to bump up my flour’s overall Protein content. The result is that the flour can absorb more moisture, and gets more stretchy and stable. Adding too much would probably make the dough tough and rubbery… but I’m kinda into that tbh. It would be interesting to see how much is too much 🤔