As I said, I don't pay rent (or HOA fees) so getting the credit card would not impact any earnings beyond the credit card. Maybe Bilt has a ton of members who, like me, don't actually rent. Also, there are probably a ton of "conservative" renters who don't want another credit card. If you visit personal finance forums, you will find plenty of people who have one or at most two cards and zero interest in getting more.

I agree that if I was a renter, I would have been more inclined to get a Bilt Mastercard, too. But if we igore the (unpredictable) rent day transfer bonuses, the earnings of the card didn't really beat other cards in my fleet (say, my CSR), so without a guaranteed SUB I was never convinced that getting the card was worthwhile for me.