AWS cloud architecture can get complex fast. Once you rotate through a few engineers or external consultants how confident are you that someone within your organisation knows exactly what you have running in your cloud accounts and are those resources actually being used.
Having up to date diagrams can be invaluable when you want to know how your networks hang together or need to explain to stakeholders what you have running and why.
The problem with creating and maintaining network diagrams manually is finding the time to do it in the first place, which is never anyone's priority and then finding the time to update the diagrams when things change (which they invariably do)