Here's a super simple bash script to enable VPC flow logs on every subnet across a specified GCP project with an option to include or exclude logging metadata that I wrote. It has the aggregation interval set to 10-min however, you could modify this to your needs in addition to setting additional flags available for the VPC flow log settings.
Here are some use cases for enabling VPC flow logs:
Network monitoring: diagnostics and capacity forecasting
Network traffic optimization expenses: inter-region and zone traffic analysis
Network forensics: examine compromised IPs
Real-time security analysis: SIEM integration