Why did the plains Indians live in semi-permanet homes?

Answer 1

They lived in semi-permanent homes year round in the Prairies because they were a migratory people. Of course, once white settlers came and set up the Hudsons Bay posts all over the place, trade began to occur between Plains Indians and the white settlers, and the Plains Indians began to be reliant on the goods they got from the Hudsons Bay company. Once this happened, they were no longer migratory as they relied on the Hudsons Bay company's goods, and so they stayed where the trading posts were so that they could trade with the Hudsons Bay company.