A data engineer is working with a streaming job that updates a Delta table named 'user_activities' by joining a streaming Delta table 'activity_logs' with a static Delta table 'users'. They observed that adding new users to the 'users' table does not automatically update the 'user_activities' table, even when there are activities for those users in 'activity_logs'. What is the most likely explanation for this issue? | Databricks Certified Data Engineer - Professional Quiz