As I have spent much of my time in forward planning here in California, I can tell you that the trend toward 'curbside' mailboxes began in 1973 during the first oil crisis. At that time, the United States Post Office began requiring boxes to be placed at the curb to reduce delivery times and--what was most important at that time--gas usage for the US mail trucks.
In 1988, the US Post Office again began amending their requirements for postal boxes, and (at least here in California) began asking developers to place "gang boxes" (the multiple unit boxes) within the community rather than curbside boxes. The gang boxes allow the postal worker to turn off the engine, exit the truck and deliver mail to only one point--the place where the gang boxes are located.
Today, almost every state's Uniform Building Codes (UBCs) require that the US Postal service approve both the location and number of boxes on a site before issuing their approval for delivery. If the developer fails to comply with the location and access point for the gang boxes or if homes do not sell quickly enough so that there is 50 percent of more residents in a community, the Postal Service will refuse to deliver mail to the site, and this has created many problems for owners who have moved into new communities where the developer is having a difficult time selling the available inventory of homes.
Thanks again for your post and I hope this answers your question.
Grace Morioka, SRES, e-Pro
Community Association Manager, Consultant and Forward Planner
Area Pro Realty, San Jose, California