Its one of those gimmick sale days like "Black Friday", "Cyber Monday", "Back to School Blowout", etc. The only difference is the sales have historically just been on junk[1] rather than desirable items.

[1] Unless you are the type who needs a 55 gallons jug of lube. https://observer.com/2015/07/at-1k-55-gallon-bottle-of-lube-...