If you want to populate somewhere, how about Canada and the unpopulated, beautiful plains out there to the north. It is already colonized but has virtually zero population density. The fact is people don't live there for socioeconomic, environmental, and political reasons. I don't think populating Antarctica and Siberia holds much value except as an experiment. There are plenty of places for people to live in.

If you refer to turning Siberia, Northern Canada, Antarctica into a useful piece of agricultural land, yes that theoretically has value, but I doubt is practical given the risks to our climate. Plus I hope advances in agriculture and mining will not require terraforming those regions.

I think the main value of going to the Moon, Mars, or Venus is to have people be on multiple terrestrial bodies to hedge some extinction risk, to begin some sort of space exploration infrastructure in the future, and maybe find significant economic value in mining. We need those benefits even if we haven't colonized or terraformed all of Earth.