afaik, thats so the device can format the card in its preferred filesystem. Instead of pestering the user (who may only use their computer as a "Facebook machine") to make sure they format the card to X specification, the device can just do that for them. Outside of "that", the device isn't doing anything special during format (unless its using the "secure" bits of a SD card, which pretty much no one does).

However, as at least some of the devices users will be Windows users, it does tend to limit the FS choices to FAT, exFAT or NTFS if the user expects to treat the card as removable storage to transfer files, like in a digital camera, so the issue is pretty much moot. Unless MS are still charging royalties on FAT and the device manufacturer wants to avoid those.

These days with people mainly using their phones, and the transfer of files being done over the air, allows device manufacturers more freedom with their SD card FS choice.