>The thing I find interesting about a lot of things like this is that they feel like a holdover of half the era where negotiating prices was normal: today, for most people in the US, most shopping is just a matter of going somewhere and paying a set price and you don’t argue with the seller to get a better one. B2B transactions still usually involve a negotiation, I think, but it’s basically gone for consumers.

Not really. The "negotiation" is still there. Time limited discounts weed out consumers who need something immediately. Coupons weed out people who aren't willing to put the legwork to find them. Loyalty programs and app-based offers (eg. McDonalds) take all of this to the next level by sending targeted coupons based on whatever demographic/behavioral information they can glean from you.