After the first Dalki war, Earth didn't have as much land mass as it did in the past. This led to gigantic highrise buildings surrounded by walls. Since the war was going on at the time, it also allowed protection in case of an attack.
Due to the low population of the human race, the little landmass worked out better for them. However, the current time was not like that of the past. In the past, only the wealthiest people could live on earth, while others would have no choice but to live on the beast planet's solar system.
Now though, Earth had once again become a type of battleground. More so in a political sense, but extremists in each group would constantly fight against each other, leaving those on earth as some of the strongest in the solar system.