From anecdotal evidence I don't think you're right. Every summer I speak to an average of three strangers a week that stroll by the harbour and ask about how to get a space, how to buy a boat, and how they can go about doing it. But very few people take the plunge. When I tell people how I live most of them are envious (some think I'm crazy too).

I think what's keeping people from doing it is fear. Most people don't have the courage to break with deepheld norms such as living in a house or an apartment.

I also live on a boat, in France, and the pressure on mooring places is unbearable in many places, including all of those conveniently close to "good" jobs. This is worsened by the waterways administration's Kafka-like madness. For instance, a boat which has mooring rights in Paris will cost about €600K more than the same one in an unremarkable place (mooring rights are effectively attached to a boat, and non-transferable).

So more extensive evidence shows that when living in a boat becomes popular, prices (in money and inconveniences) do skyrocket.

No, I do think he's right. They might be honestly curious about the details of living on a boat, but in the end not really that interested in pursuing it for themselves. Many think of it as something they might really like to try out for a year or two... tops. others, likely see the appeal but realize that it's not a realistic option for them (spouses, children, pets, etc.). If everyone wanted to live on a boat too, there is no way your costs would stay the same (slip costs would go through the roof).