My sims rarely stay in one place for the entirety of their lives. Mine usually live in different houses at different times in their lives, starting with starter houses and moving as their family expands. I usually have a specific "dream house" for them to aspire to, and it takes them a while to get there.
Also, I just get bored of the same scenery after a while.
In my alien legacy, my founder started in StrangerVille, and moved around throughout his life. I always had the goal that he would move back to StrangerVille because it felt like home to him. That's the closest to my sims staying in one place I've ever really been.