Ok people, individuals who can't or don't work, obviously have no personal income to be taxed. We and the government assume that they are dependent on somebody else, be that a family member, parent, spouse, boyfriend, girlfriend, etc.

The reason you would need an ITIN to do your taxes is because the government assigns everyone a SSN shortly after birth and this is a way for the government to assign its citizens a national identity (even though that wasnn't it's original purpose). In the US, your SSN sort of acts as your national id card. The number can never belong to someone else. It is as unique and personal as your own identity. If you don't have one, then your ITIN becomes this identifier for TAX purposes only.