Appreciating property values and high-paying jobs in desirable locations with lots of fun places to dispose of your disposable income?
The article says they're paying rent, so in that situation they're causing a landlord's price appreciation. Millenial home ownership is historically low (in modern history), so they're not building equity, or getting a mortgage interest deduction. They're also paying high rents because they're in urban areas to offset the higher paying jobs.