I think the average data team at a startup using something like Redshift/BigQuery/Snowflake is using window functions quite extensively when writing analytical queries/building data pipelines so I'm surprised to hear you haven't see much customer demand for them.
If you trying to wholesale replace a "traditional" batch oriented data warehouse like the ones I mentioned above I think building support for window functions would be essential.
To be clear, window functions are definitely on our radar! But you’d be surprised how many folks are delighted just to have more basic SQL features, like fully functional joins. Streaming SQL is surprisingly far behind batch SQL.
If you trying to wholesale replace a "traditional" batch oriented data warehouse like the ones I mentioned above I think building support for window functions would be essential.