Emulsifiers are fundamental in the formulation of cosmetics
Water and Oil do not naturally mix together. It is the job of an emulsifier to make this happen. A cream is simply the emulsification of oil and water.
Can you just use one emulsifier?
Every emulsifier has slightly different properties from their emulsification strength, feel and skin properties. It is rare that a single emulsifier will create the feel and stability you are looking for, so emulsifiers are normally combined.