Service Packs vs windows updates and patches

We are undergoing a Security Audit of our internal computer systems by an external 3rd party auditor.
We just rolled out new Windows 10 PCs to 75% of our staff and everything is working great.
We use Ivanti for patch management and all PCs are fully patched with all Windows updates and application security patches.
My question is:
What benefit , security wise, is there in ensuring that Service Packs are all completely up to date?
i.e. Does Windows 10 Service Pack 1909 contain more security patches or benefits if all individual Windows updates and security patches are already up to date?
I'd rather not install the Service Pack since all is working fine.

Thanks!