Firstly, you can't buy juice of this quality anyway in Australia; cold pressed, organic, delicious (ie doesn't taste like kale mixed with water) and in glass bottles. There are a couple of exceptional juice bars in LA but we'll happily enter our stuff into the World Championships.
Most bottled juice at supermarkets or cafes are pasteurized, a process that heats the juice to high temperatures. These juices have a lifespan upwards of 50 days so the company isn’t in such a rush to sell them. However, the drawback is that these methods basically sterilize the juice, destroying live enzymes and nutrients, and minimizing flavour.
Similarly, any juice that use the common centrifugal juicer (like juice bars that rhyme with Overproduced), are destroying some of the enzymes when extracting. Heat and oxidation from fast spinning blades damage the cells, extracting a lot less of the nutrition. Any juice made 'fresh' in a cup has a 10-15 minute shelf life because oxygen is aggressively attacking the nutrients.