I would suspect that most instances of SQL Server support off-the-shelf applications that require SQL Server rather than custom built applications.
Of course, a lot of these come from Microsoft - but there are a lot of 3rd party applications that support SQL Server. There are also a lot of advantages of standardizing on a single database platform within an organization.
Of course, a lot of these come from Microsoft - but there are a lot of 3rd party applications that support SQL Server. There are also a lot of advantages of standardizing on a single database platform within an organization.