Perhaps this has been mentioned and I missed it, and in any case there is no way to quantify it, but I wonder if education debt plays a part in this? The millenials are the ones now actively in the process of having to pay off six figure student loan debt.
I finished college and graduate school, both paid for almost completely by me rather than my parents, with debt of less than $10k, and half of it was cancelled because I went into teaching.
By contrast, I have a 35 year old nephew; he and his wife (who also went to law school) have nearly $200k in education debt. This level of debt to me would be soul-crushing, but they don't seem alarmed, probably because many of their friends have similar debt levels. But in any case, their ability to pour disposable income into leisure pursuits is limited, and will be for years to come.