It's not just people who own houses that have to move between them. Most millennials haven't even bought a house yet. But they still need to move between apartments, and that happens on more frequent time scales than someone buying/selling their home. If I had to guess, the average lease in a city for 20-30 year old tenants is between 1 and 3 years. It's not uncommon to move three times in a five year period.
Part of it is that, if you're single and renting, you're probably more likely to move closer to a new job to avoid even a relatively modest increase in commute time. Whereas, if you own a place--especially if there are other considerations like a partner or kids--you'll likely just suck up a longer commute to stay where you are.
I have watched most episodes of Shark Tank. I remember than when a 'pitcher' starts with the phrase "XYZ industry is a $$$$ billion business in the U.S., look like an upcoming target for disruption", the sharks start rolling their eyes. That person usually doesn't get the funding.
> As we've reported, Americans are generally moving less
We (the people not living in the USA) think that USA residents buy and sell houses 'frequently'. Buy --> wait --> price goes up --> sell --> buy the next house.
I think that a critical contribution to moving less is the financial crisis 2008-2018 it would make sense that people were stuck to the houses they bought, unable to perform the aforementioned loop, thus moving less.