This is indeed so basic and simple and I got surprised when I observed during one of my assignments that the customer has not set a default measure for the cube; they just did not know about this option. Since when you browse the cube, a default measure is picked up automatically and that suits the requirement of the client But what if you want a different measure to pop up by default?
This is where you set the default measure for the cube:
As per the documentation the SQL Server Analysis Services may pick up any measure as the default measure if one is not set (I generally see it picks up the first measure). In the above example, Total Sales could be a good default measure and gets picked up automatically being the first measure in the measure group. But what if you wanted Unit Sales to be the default measure; then, you need to set this explicitly.
Yes, I know simple stuff, but I still see customers ignoring this or not knowing about this.