Purpose of Data Warehousing?
As a BI consultant, my view on datawarehousing is that it provides (primarily) non-technical users with an easily accessible set of facts and dimensions.

Often, you'll see the following features in a data warehouse:


denormalized dimensions,
simplified fact tables and measures,
pre-aggregated balances,
pre-accumulated amounts over some time dimension,
often with some business logic (distributions, calculations, statistics) already applied to the data,
dimension data organized as a hierarchy where originally wasn't,
etc


All of this serves to simplify the understanding of, and accessibility to, the business data for people who aren't too comfortable writing SQL queries or using pivot table tools. Some of the greatest pitfalls in data warehousing and BI involve users not understanding the structure or meaning of the data, producing incorrect results and subsequently not trusting the BI solution.