When you are monitoring your AWS infrastructure for security alerts, not all security signals can be remediated automatically. Large or complex environments can generate multiple security flags (repeatedly) that need to be manually investigated in detail.  This requires access to sometimes complex metadata to thoroughly investigate which may place a strain on your in-house security skills or may even require you to find the budget for a dedicated security expert.

Security is possibly the most important consideration for any organization storing data or hosting applications on public cloud infrastructure.

S3 Optimization

Some organisations struggle to contain their S3 Storage costs through a combination of failures around planning and monitoring. This could be due to the complete absence or incomplete application of both important steps.

AWS security groups act as a virtual firewall for your EC2 instances to control inbound and outbound traffic.

"Security groups act at the instance level, not the subnet level. Therefore, each instance in a subnet in your VPC could be assigned to a different set of security groups." -  AWS Documentation