Probably there to both minimise etching time, and to ensure that, even with a very poor process control ( likely if the PCB is being made by a lot of labour, and not in an automated controlled bath) they will have enough trace left to both solder to, and also a wide enough trace so that shipping vibration will not peel them off the board. All 3 look like they are made with SRBP, and thus made cheaply, so likely in a building without any temperature control, other than a fan for the workers in hot weather, and a coat in winter. Massive variation in etch time, and they probably etch till the outer board is fully clear, then give it a few minutes more in the tank with the bubbler on, to get the inner ones, thus overetching the outer ones. Then wash, clean with some scouring agent ( could be a pad, river sand or even silty mud, you never know), rinse, dry and screen on the solder mask, and then either they have an old NC drill to do the holes, or there is a drill press, a stack of boards, and a mask, and somebody doing it by eye, so you want a good amount of pad around the traces in case the drill is a little skew.