Two reasons for the lack of 2* - 2.5* reviews in NYC:

1. You might be OK bidding a 2* in some midwest suburb (although I've been burned) -- you'd probably get an EconoLodge or something. In NYC you could well get a genuine hellhole/rat's nest. I don't bid less than 4* in NY myself.

2. The kinds of people who frequent BFT and BB are more conscious and involved travelers, and IMO more likely to bid to avoid < 3* properties.