If you live near a large body of water, activities on the water are fairly common. From wakeboarding to fishing to just sitting out on a boat in the middle of the ocean or lake to have a picnic in the sun, boats are pretty ubiquitous culturally around waterfront areas. It's like asking why people own beach towels or swimsuits when they live near a beach.

Do you live anywhere near water? Move closer to water. You will meet people who have boats.

Same reason people buy motorhomes - this just moves on water. It's like a second home you can go to on holidays. Our first one was just a small fibreglass hulled boat for day trips but every subsequent one after that has been bigger than the previous. The current one is 11 meters long steel boat that weighs over 10000kg and has most modern comforts you'd find on a house or summer cabin: heating, running water, indoor toilet, sauna, solar panels, full kitchen and so on.