Heat conduction is very poor; you're practically in a vacuum, so you can only lose heat by radiating it. On earth, you can dump your heat into the atmosphere o

Heat conduction is very poor; you're practically in a vacuum, so you can only lose heat by radiating it. On earth, you can dump your heat into the atmosphere or the oceans, which are both gigantic heat sinks. The entire surface of the earth then radiates that heat out to space. In space, you only have your own surface to radiate the heat out.