Why doesn't all of Alaska have cold, snowy winters?

Well Im not sure why you think it doesnt. The northern towns like Barrow clearly do, as does towns in the center like Fairbanks. Cities in southcentral like Anchorage have cold snowy winters. Even the southernmost cities like Juneau have winters with average temps below freezing. All of Alaska has cold snowy winters. Of course, not to the same degree, but that's because Alaska is a huge state. It's like asking why different parts of the country have different weather...because they are not in the same place.