If a person buys a home most of those people don't stay in there home longer than 15 years.
Some people who get a 30 year mortgage will sell there house and move by 15 years at the latest and sometimes people move to a new house 13 to 14 years after getting the home mortgage.
Not everyone moves out of there house after a certain amount of time.
My Grandma has lived in the same house she bought 40 years ago and plans to stay there until she dies.
I've lived in my current house 10 years and I plan to stay in my house until at least the mortgage is paid off in 20 years or maybe sooner but then again I may decide to just stay here the rest of my life.
Some people move on because they get tired of the same place or they need to move because of a job.