I suspect its more about market segmentation. Its a slight hassle to use the app and if you want those great deals you dont get much choice in what you can orde

I suspect its more about market segmentation. Its a slight hassle to use the app and if you want those great deals you dont get much choice in what you can order at a discount - the discounted menu items rotate frequently. So people who have more disposable income wont make a habit of using the steep in-app discounts and just order whatever they feel like eating at MSRP.