Cashback is credited for booking of hotels and apartments only.
It used to be interesting but now it's becoming unprofitable. Before switching to Letyshops, booking often offered an 8% discount. Since I activated letyshops, there is no longer any discount and letyshops can only give 2.6% cashback. Not at all profitable.
We totally understand your concern and hope that partners will increase a commission as well as our customers do. Regarding discounts offered by Booking, partners provide special discounts for certain groups of customers, and these discounts are not always compatible with cashback. Of course, you can choose the most favorable way to save money for you.