Having an 8GB eMMC does not preclude having an SD slot. Any beginner can plug in an auto-installer on the SD card and use the same SD for different devices. Simpler and cheaper.
If that's not enough, the eMMC could even come preinstalled with an OS.
Having soldered eMMC also means that you have complicated the effort required to securely wipe the device. It doesn’t get any easier than ejecting an SD card.
If that's not enough, the eMMC could even come preinstalled with an OS.