The Gus!

This one you can't see very well, but I think it's a good example of why you wouldnt bag out a gusset- it takes away from the front design feature of the garment if it were to be bagged out, but as an overlocked peice it remains invisible and flat

A brief with an overlocked gusset- This one was a very short gusset, it ended before the elastic came together a the back, which was uncommon amongst the styles I saw. It left a tiny gap, that you can see right next to my thumb... not damaging, but probably not functional or beneficial (prehaps they had to cut back on fabric for cost reasons!)