In spanish it is interchangeably called castellano or spanish. Outside Spain it is always called spanish.

The same way valencian is decidedly called valencian in Valencia, but people from Catalonia insist on calling it "simply a dialect of catalonian".

The same way hispanics in America are called "latinos", while americans with italian and french heritage are not.

The same way americans with english heritage aren't called "anglos" but simply "americans".

Once you begin actually looking at the language used you understand that it is NEVER unintentional