I don't see that as making this a very fair system. Many of my colleagues had parents refuse to pay a dime. I know they were hurt by it and some actually had to wait until they were of age to be an independent.
Private schools cost money. Somebody has to pay and it isn't the state. If your parents don't want to pay for a private education, then take it up with them. It's fair from Harvard's perspective and the perspective of the general population.
I wasn't aware of the voting that took place to find out what the perspective of the general population thinks. The university I went to was public and the age for being an independent was for federal student aid. Seems like it doesn't matter if something isn't fair.