Why cookiecutter-django does not set DATABASE_URL and CELERY_BROKER_URL during entrypoint execution?

cookiecutter-django does not set env variables for DATABASE_URL and CELERY_BROKER_URL during "entrypoint" file execution in local development environment.

After I manually 'exported' DATABASE_URL and CELERY_BROKER_URL they appeared in environment variables. Why is that?

By manually I mean I got inside the docker container then on the shell I wrote:

export DATABASE_URL="postgres://${POSTGRES_USER}:${POSTGRES_PASSWORD}@${POSTGRES_HOST}:${POSTGRES_PORT}/${POSTGRES_DB}"

and

export CELERY_BROKER_URL="${REDIS_URL}"