Without the added quotation marks, the following error is thrown:

"failed parsing config: /etc/loki/config/config.yaml:  Use `-config.expand-env=true` flag if you want to expand environment variables in your config file"

So without this change, the examples are not working properly.

In https://grafana.com/docs/loki/latest/operations/storage/tsdb/ the quotation marks are also used.