So much of the most comfortable housing stock in America is single-family "McMansion" type homes. The type of suburban detached house that likely the majority of middle-class American millennials grew up in.

For a young adult in the current economic climate, the only way you're living in one of these cushy homes is if you're living with your parents.

You can't rent one very easily, since they can't be divided up into multiple units or rented at all due to zoning and HOAs. Not to mention it's not typical to be a renter in these neighborhoods to begin with, so even finding a rental is nearly impossible in some areas.

Then of course, after the housing bubble crashed and the subsidies went away, a mortgage for one of these became a big challenge to achieve, and who has the savings sitting around for upkeep and emergency maintenance?

Boomer parents, and a handful of lucky gen-xers are pretty much the only people who could comfortably acquire and hold onto these houses, so it only makes sense that sticking to them like glue is the best strategy if you wanted one.

And there's also the fact that it's just not cool to live in the 'burbs, where you grew up, in the first place. The mental justification has to be "well I'm saving money at least". Saving money, means crashing with the parents. After all, it's "just temporary".

Those are at least my very subjective observations that might be overlooked in that study...