using microsoft.visualstudio.testtools.unittesting not found code example

Example: Unable to find package 'Microsoft.VisualStudio.TestTools.UnitTesting

Just had this issue, and this answer was the solution. Anyone have any insight as to why this is the case? Why is the namespace Microsoft.VisualStudio.TestTools.UnitTesting and the assembly is Microsoft.VisualStudio.QualityTools.UnitTestFramework? Why could they not name them both the same thing?