On this note, I'm actually confused about why datacenters raise electric costs. Why doesn't the data center bear an extra cost for the added infrastructure?

If I build a house on undeveloped land and the electric company needs to run lines, do I also (in a much smaller way than a data center) increase the costs for all other customers? Is everything always just spread evenly?

In many places there is little excess capacity. Many protesters know that their electricity prices, like gas prices, will soar and price them out of AC.