The real question is "why do rates go up with a data center?"
That answer is interesting. Its cause in most states, if a company formally requests a power hookup, the power company MUST comply. Thus entails in upgrading substations, transformers, supply lines, etc. And all those upgrades are borne by the citizens in that region.
That's why you bill goes up, cause datacenter upgrades dump on the public their externalities.
In some states like Indiana, the governor is already talking about changing that law requiring data centers to pay for upgrades.
Every place I'm familiar with has demand charges on large-scale users that is supposed to pay for that equipment.
The real problem is boomers have stopped allowing things to be built efficiently, so supply is limited, had been limited for decades, and demand still grows, so prices spike disproportionally with demand increases.
Additionally we subsidize wind and solar heavily, but the fixed costs of large plants don't drop, so we end up spending for our power twice and for natural gas plants to replace coal, because that's the only solution we will do to keep power during the winter in Northern states.
If you want fiber connected to your building you have to pay for the infra to be upgraded. Passing on the cost to other people does not have to happen (unless there is a law).
The rules shouldn't be specific to datacenters though; mechanics like Pennsylvania's "but-for" cost allocation make sense globally. If a new smelting plant requires upgrades to a substation, which wouldn't otherwise be necessary, the smelting plant should be charged accordingly.