Edit: yugi beat me to it...

GGR = Gas, Groceries, and Restaurants

This is definitely true, and card issuers have taken action based on the activities of churners. From a business process perspective, it's generally a bad idea to change a process due to outliers. While churners (or optimizers if you prefer) have the appearance of an outsized impact, we typically don't have a visible impact in the aggregate. In the case of Bilt, I imagine that one of the reasons why churners do have a material impact is because there are likely few non-churners applying for the Bilt card. Even without the Rent Day bonus, it's still a great card considering that there is no annual fee and there are some great transfer partners.