File systems for embedded systems and IoT devices have some additional requirements:

Power-cut resilience - it requires strong guarantees that the file system remains consistent, and data is flushed to the underlying storage.
Wear-leveling - typically storage supports a limited number of erases per block, so making use of the entire storage device is important for reliability.
Tiny footprint - IoT devices are constrained by ROM and RAM. A small footprint saves money.