Without this essential step, the cream cheese may not fully combine into the soup, leaving little bits of undissolved cream cheese floating around in your broth.
Cheese is a particularly tricky addition because if the temperature of the soup is too hot or too cold, the cheese won't melt properly and will start to clump.
When it comes to potato soup, the emulsification process is slightly easier. Potato protein works as an emulsifying agent that helps suspend fats and liquids together.
However, the smaller the droplets of the two substances are, the easier they can form a cohesive result, so the blender breaks down the cream cheese for a smoother texture.