re:
Welcome to Android Central! There are many many words written about the advantages and disadvantages of SD cards, and it probably isn't worth recapping them all here. One of the reasons not to include SD cards is the not insignificant rate of SD card failure (due both to poor quality cards as well as poor implentation of the SD interface, which is manufacturer-specific), which can then lead to much gnashing of teeth after losing all of the precious data that may have only been saved to the card (and not backed up anywhere).