After WW2, the city suffered from a housing shortage and lving on water became popular. The Dutch saw an opportunity in retrofitting a surplus of old cargo ships into affordable living spaces.
Also, Amsterdam has laws about the houseboats and the wooden ones need to be repainted every three years.
The houseboats in Amsterdam are permanently anchored to a specific address. A special permit called a ligplaats entitles a houseboat owner to moor their home in a certain spot. These permits are in high demand, and as with all properties, a prime location significantly increases the value of a houseboat. - holland.com