The main reason to make a module variant for a SoC really is integration into your own hardware projects... a lot of embedded systems for all kinds of applications need some higher level system running a OS like Linux for UI/networking/communication functions while the rest is done by specialized hardware (control systems, machine interfaces,.....). Designing in and obtaining a SoC like the A64 is a risky, time and cost ineffective path if you don't have some higher production volume... so you usually get the SoC with all the components that are required on a module and put that on your custom hardware design. This approach usually makes it also easier to upgrade in the future. There are whole companies in the embedded systems field that specialized only in making families of modules that are interchangable like Enclustra, Toradex or Phytec, to name a few...
Come have a chat in the Pine IRC channel >>