I cannot speak as to why others live aboard their boats nor can I explain the eccentrisities of other sailors. I can share why my wife and I live aboard our boat.
The biggest thing was wanting to get out of the rat race. We saw our friends buyng houses they couldn't afford, cars whose monthly payments were equal to slip fees, and the general desire to accumulate "stuff." We saw that living aboard to prepare to go cruising would help us know the boat better and be better prepared when set out over the horizon.
The next thing is the family we plan to have. When we look at the public school system in America and scores keep dropping the choice was a no brainer. We dont want our children to be immersed in the MTV generation crap. We have chosen to spend the next 5 years or so doing an extensive refit of the boat. Once the munchkins are tall enough to see over the life lines were taking off cruising. We would like our children to experience the world not a small enclave of some suburban neighborhood.
"A boat really does represent freedom. Freedom to set your own course, or drop the anchor and observe the beauty around you."