Listen, I didn't curse ALL the cities. I captured the first one, and somehow cursed it without even realizing how. The rest of them remained Titan cities...
In principle, it's not necessary to do that. That's what I think.
I cursed everything because I had nothing else to do. I had to wander around for several months until I got all the dark and summoning spells in the treasury and pyramid. I had a very well-leveled Godric. So, going to him without strong magic was useless.