It becomes more funny once you shift online. Basically every checkout has a "coupon" field.

Now you look for coupons, and some coupon aggregator of doubtful quality pops up.

You find something that works. Or give up. Done.

The coupon sites are usually of doubtful quality because .... Basically all affiliate networks forbid it. It's also the reason why "last click" attribution is horribly broken.

Funnily enough it's now mostly magazins & newspapers that run these coupon sites in Germany.