Using SSAS for retrieval data instead of using SSRS to make a report?
Depending on what type/volume of data you are reporting on, SSAS can possibly make it easier. I would not take that as a blanket statement. The decision to generate reports off of a relational or dimensional database should be made on a case by case basis.

Keep in mind that the development required to build an OLAP database around a subject area is far more time consuming than building a single report (or even several). 

The benefits of building out an OLAP database are huge in return. In many cases, your users can connect directly to it with excel and generate their own reports. This eases the SSRS development requirements on IT.

At the end of the day, there are many factors that would contribute to answering your question. There is simply not a one size fits all solution.