Motive behind functional coverage at SOC level and motive behind code coverage at SOC level

Could you please clarify the following.

at the SOC level verification we need to see whether pins are exercised. for this toggle coverage of pins at the SOC level is enough. please let me know is there any other motive is there behind toggle coverage at SOC level. or any other code coverage is required. and why we need functional coverage at the SoC level. can we reuse the code coverage at IP level,at the SoC level.similarly can we reuse functional coverage at IP level at the SoC level.