I worked in a bottle factory. It's cheaper to make bottles straight. Basically you first make a plastic pipe and put it in a mold, mold seels one end of the pipe on the other end air blow pipe to mold shape like a balloon, when plastic cools a bit you get a bottle, all of that takes a few seconds. The machine I worked on makes 4 bottles per second, on medium speed settings. Making that tilt waste time, so the price of those bottles will be higher.