For the sake are squashing the idea that the carriers take the builds and “add” software to the firmware and that takes a month, this isn’t true. At least not in a literal sense that the builds are some how charged when they come from Samsung.

In the US for example. Aside from changes specific to mobile radio firmware, carriers all have the exact same build. People like to assume Samsung cranks out a build and hands it to the carrier then the carrier modifies it. That would be a quality control nightmare considering Samsung is ultimately held accountable for the software on their devices.

Well how do you get carrier software, to include system level apps like visual voicemail and messaging apps to appear then?

This is where DT Ignite comes into play. At the time Samsung generates a build it includes this software that can read the CSC files and the sim card and make a determination of which carrier related changes, limitations, and software to implement.

This means the build that Samsung sends to the carrier isn’t then being modified again, at least not from a software design standpoint, DT Ignite already exists on the phone. Yes your phone does change based on the carrier sim but this is based on a response from software already on the Samsung firmware when it leaves Samsungs servers. This has allowed Samsung to move to unified builds for their devices years ago without worrying about generating a build for each carrier separately.

Why make say five builds when you can remotely control the software each carrier installs after the fact during the first boot when the sim card is read.

This is also why some SIM card changes will trigger a full wipe.