Thanks for asking this!
Lubrication is important during sexual contact. Although vaginas and penis’ are self-lubricating organs, often times enough lubrication is not produced. Some bodies self-lubricate quite a bit; some don’t at all! Lubrication will lower the amount of friction during intercourse, reducing the chances that a barrier method (like an external or internal condom) will tear or that a mucus membrane (like the vagina, penis, or anus) will become irritated.
Even if your body does self-lubricate, it’s great to have a bottle of water-based lube on hand just in case things become dry and uncomfortable.
So this is why someone may use lubrication. What kind of sex you use lubrication for, how much lubrication you use, or whether or not you enjoy/ don’t enjoy using it, is all up to you and your partner!