You are correct that schema-less systems can still require maintenance. However a schema-less system like Drill allows users of the data like business analysts to write interactive queries as soon as they bring new files into HDFS. Surely if you were using Drill to query data programmatically, you would want to make sure only the technical staff could modify the data during the dev process, and likely use an automated process to incorporate data as it comes in. However, this is no different than managing appropriate permissions on a traditional database.