Why is the RDS Certificate authority default still the rds-ca-2019?

When provisioning an RDS instance with MariaDB through the AWS Console or CloudFormation, the default certificate authority is set to "rds-ca-2019". It's important to note that this certificate is set to expire on August 22nd, 2024. Prior to this expiration date, it will be necessary to initiate a reboot. If not done manually, AWS will automatically reboot the instance to apply a newer certificate. It raises the question: Why isn't a certificate with a longer validity period set as the default? This would eliminate the need for an additional reboot shortly after the RDS instance is created.