One could maybe argue that there has to be some fundamental asymmetry between matter and antimatter. If there were none, you have to find a good explanation why

One could maybe argue that there has to be some fundamental asymmetry between matter and antimatter. If there were none, you have to find a good explanation why there was not the same amount of matter and antimatter right after the Big Bang and why therefore not all matter and antimatter just turned into photons leaving behind an empty universe. If on the other hand there is an asymmetry and matter is favored over antimatter, then the matter we see today would just be the difference left over after all the antimatter annihilated. In that case there seems to be no obvious reason why regions should form.