ROP gadgets, and data strings/buffers - you might have a printf format string to feed into system() that you wouldn’t have had otherwise and might not be able t

ROP gadgets, and data strings/buffers - you might have a printf format string to feed into system() that you wouldn’t have had otherwise and might not be able to supply with your shell code; also, ROP gadgets aren’t very unique, but often system and library calls are available in libc() or some other library; approximately 1% of programs I write needs system/exec calls - but it’s always there in libc making it easier to return to / exploit.