Why Does My City Feel So Empty?

I've been working on a city for a while now, and I have about 131K population. But my city feels so empty. I've been building so much road infrastructure, but everything feels incredibly overbuilt if there are no cars on the road, and it takes some of the fun out of the game. I don't know why my city feels so lifeless despite having so much life. My theory is that the game is deliberately simulating less people, so that my CPU does not explode. The only other theory is that there is not enough parking. But if I put parking anywhere, even if I make it cost $50, all the parking gets full. If that's the case, then it makes the game much less fun than CS1.