The weird thing is that there absolutely are standards, not least an obligation to make sure that what you’re selling is safe, and assembled correctly. If a bike shop sold bikes in this state they would – quite rightly – be lambasted.
Sadly it probably takes an accident happening for anything to be done about it.
What shocks me most is how un-trained the staff must be, if something so glaringly obvious is wrong. What else is not done correctly? In my experience most inexpensive (proper) bikes need a few bits and pieces doing to make them suitable for sale – surely these BSOs need more work than the average £300 bike (wheels truing, brakes setting up correctly, gears indexing) – if the forks are on back to front, it surely goes without saying that none of that has been done.