Moisturizer.....Why do you have to use it?

Moisturizers are basically just oil. You spread them on your skin and it hinders the loss of water through your skin, reasons being:
oil floats on water, oil does not evaporate easily,and water stays trapped between your skin and the oil,and therefore your skin gets to be moisturised! Thats all!. Moisturizing creams do not actually ADD moisture to your skin, but they do hinder the loss.
Moisturizing your face keeps the oil levels in your skin regulated.
Do you need to moisturize your face if you have pimples?
Usually people with oily/acne prone skin tend to use deep cleansing/acne products and wash their face daily to keep the oil under control.However,this process dries out their faces and they do not moisturize because they think it will just make their skin more oily. In reality, the skin will sense the drop in essential oil the face needs to keep hydrated , and this signals the skin to produce more oil to replenish the essential oils which leads to excess oil on the face.So when you moisturize your skin,it keeps the skin from producing excess oil.