I can't really tell if you're joking, but I think your question illustrates a different flaw in the article.
People really write about the databases you listed, because their users have an entirely different mindset. Sure people may switch from Oracle to DB2, or from SQL Server to Oracle, but some organisations just have "standard databases" that they work with. Switch would be a multi year process, and certainly not something to be advertised, unless it's: "Now with support for SQL Server" in the marketing material.
People really write about the databases you listed, because their users have an entirely different mindset. Sure people may switch from Oracle to DB2, or from SQL Server to Oracle, but some organisations just have "standard databases" that they work with. Switch would be a multi year process, and certainly not something to be advertised, unless it's: "Now with support for SQL Server" in the marketing material.