ip

IP packets have a size limitation (65,535 bytes), so a reassembled packet is limited, and the application would need to send chunks no larger than the theoretical IP packet payload size (total packet length minus the packet header for IPv4). On the other hand, TCP can handle an arbitrarily large (mega-, giga-, etc. bytes) data stream by segmenting it.

Also, IP fragmentation has fallen out of favor because of the resources used by the intermediate routers necessary to preform the fragmentation, and the possibility of fragment attacks on the destination hosts.