They don’t seem to get that in a few years, millenials will be approaching 40, will have been in the work force for 10 or 15 years, and may have an entirely different ideas about politics.
I have seen this in my own family; you advance in your career, you buy a house, and all of a sudden different things matter to you.
Ditto when you start having children. That is a major turning point in life, in which some people decide they really don’t want to raise a family in a liberal city such as San Francisco,,for example. So they move somewhere more family friendly.
The article mentions this possibility but rejects it, claiming that political attitudes are largely set in young adulthood. I agree with you, though, and have witnessed the same gradual shift to conservative views in both my and mrs riverdawg’s sides of the family.