One of the main reasons SD cards fail in a PI is shutting them down incorrectly. If you pull the power cord you risk corrupting the card. If the PI had a proper power switch system (also omitted due to cost) then you would see less SD cards being corrupted.

It is possible that even on-board flash memory could be corrupted by improper shutdown, and if that happened the entire pi would be useless, not just the SD card.