1: App knows your location - most likely is profiting from that
2: App can see how often you visit $place, all for the cost of a few 'sale' items.
3: More extensive profiling can possibly occur, depending on what data the OS allows you to access.
As apposed to:
1: Walk to shop, no smartphone, see discounts inside shop.
There's 0 reason this information needs to be presented via any form of 'notification'. It could literally be done by $shop.com/discounteditems.txt.