The “free lunch” for the coffee chains is all the customer data they collect. Most apps ask to enable notifications and location services (even if this was only used to find nearby stores while the app is open). If you want all the offers, you must opt into marketing communications. Setting up an account to order ahead, pay and collect points requires providing personal data including an optional date of birth (most chains offer a free birthday treat).
Forgo the convenience of ordering ahead, and taking a reusable cup still nets you a discount of £1 at Pure, 50p at Pret and M&S Cafes; 45p at Black Sheep...