Let me start with a little history of Microsoft BI. Microsoft acquired an OLAP tool from a company called Panorama, project name Plato, which was bundled in with SQL Server 7.0 and from this grew the present incarnation of Analysis Services which IMHO is the crown jewel in the company’s BI armory, it has allowed the creation of Performance Point, data mining in Excel, and the Unified Dimensional Model to capture business definitions and model security.
A common misconception is that you don’t have to use Microsoft tools to get at Analysis Services, because, like many OLAP engines it uses MDX as its query language in the same way as SQL is the query language for relational databases. However, just like SQL, MDX comes in lots of flavours, and has been developed by each vendor so functionality will vary from Oracle Hyperion to SAP/BW etc.
So there is a small but thriving economy of independent tools that connect to all of these engines and fulfill some niche functionality that is available elsewhere. An obvious example is that same Panorama company with it’s product Novaview which has a very intuitive web UI. Another good visualisation tool from a Microsoft Gold Partner is Tableau:
The important thing here is that the data for these tools comes from a central source and while it may make sense to give everyone access to a cube in Excel, one of these specialised tools might be the best thing for your analysts to use, if it does what they need.
Using an analogy with SQL Server (the database engine) you might want to run a third party niche accounting system or ERP system for your business, but this could well run on SQL Server, which means you can expose the data in it to Excel or Reporting Services.