As has been pointed out, "punching down' bread dough, after it has risen, is a way to release CO2 that builds up during fermentation. I find that my bread benefits from a more gentle degassing that "puncing down" implies. The handling required to turn the dough out onto the board, scale it and round it for a brief rest is more than enough to release excess gas.
As to why you might turn your dough during the first rise, one reason is to help with gluten development. By stretching and folding your dough a couple of times during fermentation you realign and strengthen the gluten strands. This is a good thing. With some doughs, like ciabatta, this folding is the only chance you have to develop gluten as the 'dough' is too wet to knead in the traditional fashion.
Hope this helps,
At weddings, my Aunts would poke me in the ribs and cackle "You're next!". They stopped when I started doing the same to them at funerals.www.kyleskitchen.net