Using SQL Server views throughout a Business Intelligence (BI) solution can provide a tremendous amount of benefits.  Here is a list of such benefits, taken in large part from the excellent video SQLBI Methodology by Marco Russo and Alberto Ferrari:

Benefit of views

• Can be modified by anyone, even outside of BIDS/SSDT
• Can provide default values when needed
• Simple computation can be carried out by views
• Renaming fields leads to better understanding of the flow
• Can present a star schema, even if the underlying structure is much more complex
• Can be analyzed by third-party tools to get dependency tracking
• Can be optimized without ever opening BIDS/SSDT
• For security reasons, to limit the rows retrieved by joining with a security table

Benefit of views in SQL Server Integration Services (SSIS):

• Simpler code inside SSIS packages
• No need to open the package to understand what it is reading
• Easily query the database for debugging purposes
• Query optimizations can be carried out separately

Benefit of views in SQL Server Analysis Services (SSAS):

• Renaming database columns to SSAS attributes
• Clearly exposing all the transformations to DBA
• Simplifying handling of fast variations
• Full control on JOINs sent to SQL Server
• Exposing a start schema, even if the underlying structure is not a simple star schema