In the US, you often get a choice (via the PoS terminal or via the person at the register) if you’d like your receipt. Whether it’s printed automatically without asking you is in and of itself arbitrary and not even consistent within a single type of business, and there are often several options (“No receipt”, “Print”, “Email”, “Print and Email”). Even if it’s printed mandatorily, cashiers will often ask if you want a receipt and toss it if you don’t. Finally, different PoS terminals have different interfaces for this sort of thing. So it’s generally not at the forefront of your mind, it’s not really standardized, and you need to quickly weigh a bunch of factors as to whether you want the receipt and often in what format, so the poster here is joking about how extemely arbitrary their answers are since it usually doesn’t make that big of a difference which you pick.