I found a Reddit thread where it said if you live in a Bilt Alliance property as a non carhdholder you only get 250 points instead of 1x.

If you generously say that the Bilt points are worth 2cpp, 24k points per year is $480 per year or $960 every two years. If you count this as one of your 4 personal SUBs per two years, you can find better SUBs than that. Not counting the 5x for the first 5 days with max $10k spend.

The other answer is ... a lot of people find credit cards scary and don't want to apply for new ones?