Sharepoint and Metadata
I always recommend metadata to improve findability and search. However, coming up with a taxonomy and information architecture seems like a chore for many customers.
I find that customer that have certain LOB, department that have their business revolve around documents will use the metadata capabilities. That is information and knowledge management scenarios. Other than, if it is just a community wiki or project documents with defined lifecycles, customers don't want to apply metadata usually. Sometimes the OOTB search is 'good enough' for them. Something to watch out for is project cortex that should come out soon which will use AI and automatically aggregate content based topic keywords, but you have some influence on the modelling with their AI Tools.
Hope this helps. Feel free to reach out.