As a millennial, here are my thoughts...
Boating is a really broad category. Most of us on the forum are interested in cruising powerboats, which is a tiny portion of the overall market, but the market I'm most familiar with.
Cruising requires time, money, and health. For millennials, health hasn't become an issue, so it's really just time and money. Most who have the time don't have the money, and most who have the money don't have the time. Cruising just isn't very compatible with full time employment.
Many of the "rites of passage"—marriage, home ownership, etc.—seem to happen later for millennials. This is for a couple reasons I think. First, millennials are seeking more education. More fields require a graduate degree, and there are many graduate degrees which simply didn't exist when our parents were in school or entering the workforce. Since people are in school longer, the rest of their lives get delayed a bit. Second, because of all this extra education, and the insane rates of inflation in higher education, millennials are burdened with more student debt than previous generations. Combine this with entering the workforce later, and it's easy to see how big purchases (houses, boats) get pushed back until later in life.
Other factors...
Many people are now hired as "contractors" working at large companies. They don't get much (if any) paid time off and they have little job security. No free time, no boat!
There are lots of activities competing for free time and money. Most of my friends prioritize really active hobbies at this stage of life...cycling, skiing, climbing, backpacking, etc. These are less expensive to get into than boating, and more physically demanding (so better done when young and healthy).
Finally...a big one...is that the boating industry and a lot of "old salts" just aren't that welcoming to newcomers who don't fit their idea of what a boater/cruiser should be. When I was boat shopping, I experienced brokers that just didn't have the time of day for me because I was "too young". I know single women in boating who use only a first initial and last name in boating-related emails so they're taken more seriously. So many "old salts" descend into condescending, scary spiels when talking with people who are trying to get into boating.
But, the big problem is not that millennials aren't buying boats, since I think that'll change as we get older/wealthier/more secure.
The BIG problem I see is not enough millennials are going into the marine trades. Most of the tradespeople I hire (and see on the docks) are 50+. Frankly, working in the trades was never discussed as a possibility growing up. Not at home, not at school, not on TV. The focus was entirely on going to a four year college, then getting some work experience and going back to grad school. Won't somebody start telling kids that there are good jobs, making living wages, in the trades, and there's nothing wrong with working with your hands or getting dirty!?!?
