That's news to me, a right to claiming all the independence and rights of an adult as well as holding the parents as serfs to work for you. If it's taken away, resentment and bitterness. If it's paid, a sense that parents properly rendered tribute.
The phrase "little emperor" comes to mind. The little middle of the little middle kingdom.
When baby boomers objected to their parents using their own money and not leaving an inheritance, they were usually considered spoiled and ungrateful. When Millennials have the same attitude, they're just "normal."
The kind of attitude that one kid I knew had is exceptional. His parents weren't wealthy, and he flat out said they decided not to get him a car. His friends were outraged, like he was denied food or shelter. He just shrugged. "They've fed me and my brother and taken care of us for our entire lives, and they're trying to save money for school if I want to." He saw the positive, not the negative. He saw what he'd gotten, not what he demanded. His parents loved him and he loved them back--they weren't just a sow whose only use after birthing her young was having a series of teats that provided milk, but when the piglets are nearly grown is just another pig.
I'd also note that a lot of the "Baby boomers voted to screw them just so that they could die with all the toys" is a fundamental attribution error. For the most educated generation in the US, you'd think they'd have a bit of basic logic. Few baby boomers believed that they were screwing over their kids, so the purpose clause as intent is inappropriate. But enemies don't make mistakes, they only have evil intent. That the Millennials treat their own parents as enemies and demand their parents' sacrifice as a kind of right just goes to the fact that many Baby Boomers did really, really sucky jobs raising their kids.