Home improvement stores generally do not meet ASTM (American Society for Testing Materials) & ICPI (Interlocking Concrete Pavement Institution) standards for compressive strength and absorption, which could cause problems with permitting, sign offs and breakage. Also, box stores only carry a few shapes and colors to choose from.
Paver Supply Warehouse only uses manufactures of high quality pavers that meet ASTM standards. ASTM (American Society for Testing Materials) & ICPI Standards (interlocking concrete Pavement Institution), and offer all a manufacturers colors, shapes, sizes and special orders.