that only exist to give housewives/househusbands something to do with their time
Definitely not - they're there to get people to make decisions that they otherwise wouldn't make, usually bad ones.
People love to get something for nothing. "$1 off a "premium" bag of wavy potato chips! Hell yeah!" No matter that the generic wavy potato chips are still fifty cents less and taste the same - it's a DEAL!
Kohls is famous for marking up their goods by 300% and then having a 30% off sale. The lines are out the door for "the savings". JC Penney tried to do away with that scheme and nearly went bankrupt. They went back to it this year and are returning to profitability.
If you don't have a concrete estimate of value for what you're purchasing, you can get wildly abused by the marketeers. That value will be subjective, but you better darn well know what it is if you don't want to get taken. I buy clothes at Kohls, but unless I'm desperate I limit myself to the 70% off clearance rack. That's where I find my valuation meets their prices. YMMV.