Back in the paleolithic times, people had to use temporary shelters in cave's and other small buildings. They did this because they had to move so much that they did not have time to build larger shelters.
Now we can build better shelters because we don't have to move all the time
we can gain population by staying in one spot
Building permanent houses are better because you can make your house larger and stronger.
This is also better because we have more protection from animals then in paleolithic times.