Because the B80 SBS would have free transfers to the B43 and B48 in Greenpoint, the B44 (Local and SBS), B46, B47 and B60 in Williamsburg, the B69 in Clinton Hill, and the B37, B41, B61 and B63 in Downtown Brooklyn.
Plus it would take less time for a Sheepshead Bay customer to take the or to Atlantic Avenue-Barclays Center and transfer to the B80 SBS than to pull a or --> --> --> --> Q47/Q70 SBS. Not to mention Canarsie customers having the zig-zag of --> --> --> Q47/Q70SBS when they can relax via the B60 --> B80 SBS.