Maybe its because these posters are getting their renewed passports from the printing centers such as TPC/WPC, and APC (maybe NPC?) and/or the GPO is trying to run out the stock they have. I would imagine that these are customized printers specifically designed given the added sophistication of the engraving and printing required so this isn't something that can easily ordered. The agencies will normally only print for pick up as they are mainly designed serve people who need a passport within the next few days...