And they can't be entirely blamed for thinking that way. My husband and I would "millennials", so are his peers.
He grew up in a really nice part on the North side, in a Semi-D with big garden. All of his peers did too. They all went to good schools in good postcodes and went on to do college degrees and the vast majority is better educated than their parents and work very hard. Yet all par one couple (he went to a private school) cannot even remotely afford the standard of living their parents had. And still, this mindset of Semi-D, SUV, sprogs and golden lab is so engrained in them that it indeed is a rude awakening to see that realistically they will never live like their own parents.
Now I come from Europe, I grew up in rented apartments in some areas, single parent family and we were poor. When I moved to Ireland most people struggled to wrap their head around how this is sustainable/doable. I regularly have an argument with my in-laws because they genuinely think you cannot raise children in an apartment setting.
Apartment living has always been branded as living for the poor, inferior, students and just something you do for a bit until you can buy your own gaff. And this mindset persists.
We now live in a remote location and plan to move in the next 2-3 years because we don't particularly like it but that's what we could afford. And I'd totally live in a decent apartment somewhere more built up with the children. But that simply doesn't exist, which is a shame because it is hugely efficient housing and can be done so well.