[bunderbunder]

I can't speak to document stores very well, but one spot where schema-on-read makes sense is in data warehousing type applications. One of the potential troubles with the traditional ETL approach is that transforming the data to fit a fixed schema almost always involves some information loss that might make the data less suitable for answering certain questions.

That's fine if you can predict what questions your business intelligence or data science team will be asked ahead of time, but, realistically, you can't actually do that. Using a schema-on-read data warehouse instead is a more costly option, but also leaves you more able to respond to changing business demands.