Why are people serving web traffic to a folder with a .git folder anyways? I thought it was basic deployment practice to export your code OUT of the VCS before

Why are people serving web traffic to a folder with a .git folder anyways? I thought it was basic deployment practice to export your code OUT of the VCS before deploying... every shop I've worked at had this in place. Other solutions just seem hackish to me, but every project is different I suppose.