The problem is that Google infra requires everything running to be new. There is a build horizon of 6 months. Everything built with code older than 6 months is

The problem is that Google infra requires everything running to be new. There is a build horizon of 6 months. Everything built with code older than 6 months is not able to run on Borg. And since Google deprecates many internal infra tools/libraries routinely, a team is required to make sure the service remains up-to-date. Google doesn't want to pay for such maintenance.