In space, you have to deploy all the power production you want to consume in the same package that's consuming that power.

On earth, you can build a power plant miles from the DC. And you can use all sorts of different sources of power, tidal, wind, nuclear, solar, fossil fuels. All options. And like the DC, if there's a problem with any of those sources, you can go fix it or replace it with different power sources. If there's a problem with the solar panels in space, your DC is dead.

That's both easier and a lot more flexible.