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.
Additionally, as split root storage setup because the boot partition is small is a lot more complicated than simply buying a 64GB+ sd card and (usually) have no storage problems.
This is substantially simpler for beginners than using network boot, or messing around with a bootloader via serial console.