Because there are far fewer inbound shipments, types of product can be bundled (i.e. all chems from one manufacturer in one shipment), trucks can be routed to an allowable bridge, and trucks can meet the specific transportation requirements (including exterior signage and listings of contents). Contrast that with the (presumably) many UPS trucks that go out every day with a wide variety of items. A truck may have 200 digicams on it but have to be rerouted for the 1 bottle of HC-110.
There are special shipping regs that impact B&H (and others shipping from Manhattan or Brooklyn) that don't impact Freestyle. B&H could find ways to deal with this (special shipping for hazmat, warehouse in New Jersey) but none of us know if that's economically justified. Bottom line, it sucks.