Can AWS default VPC be deleted? I checked AWS documentations and it seems the following two are against each other. So I opened a ticket with AWS, and here is their answer:
Technically yes, you can delete default VPC's and create a non-default VPC. Some services such as CloudFormer to create CloudFormation templates do searches for default VPC during creation if non-default VPC parameter is not defined. Deleting the Default VPC will not cause any underlying issue or restrict usage of any AWS service.