"It Depends". 😉

If you have de-normalized table that looks like a spreadsheet with date columns in it, queries can be both difficult to write and very slow in performance. "Normalizing" such a table to be more like an EAV table will allow for proper indexing, easy non-reporting style lookups-aggregations-etc, and still allow for some very high performance CrossTabs and Pivots for reporting purposes while also making it easier to create "moving window" reports.