Is there even enough coast for that?
If people didn't live in cities, they'd have to commute more. There would be a large increase in transportation costs.
Where I live there is an abundance of canals. "Most people" is perhaps an exaggeration, but the main points in defence of increased houseboating would be:
(1) a house is a large, expensive, immobile and illiquid asset. A houseboat is rather less expensive, which frees up capital for other purposes.
(2) the internet makes it less necessary for most people to live in cities.
(3) there would be less costs associated with moving between different areas.
As per a recent comment this thread is meant to voice contrarian opinions, that is anything this community tends not to agree with. Thus I ask you to post your contrarian views and upvote anything you do not agree with based on personal beliefs. Spam and trolling still needs to be downvoted.