Nothing is absolute!
No, it is not absolutely necessary, however, it is a very good thing to do.
The skin needs to moisturized and hydrated to stay in it's most healthy form. Without this, one will see changes such as wrinkles, dryness, looseness, sagging, and other features you may find undesirable. To answer---hydrate, hydrate, hydrate! drink plenty of water and lock in moisture to the skin with moisturizers.