NOT everyone have hair like mine, and it depends on texture, and products you're using.
Products that conditioned the hair, with conditioning formula products MADE FOR damaged hair (mine isn't), or NATURAL or organic products makes MY HAIR greasy by the 2nd day. Expensive botanical products, same thing.
If I just wash with the right shampoo, my STICK STRAIGHT HAIR, goes better the 2nd day, 3rd, 4th, 5th, even the 6th day without washing.
It is critical that you determine your natural hair type, because once you know this, you can start using products that will help you to achieve the look you always wanted.
When my hair was permed, or when they were dyed . . . . I STILL wash my hair weekly. I still uses shampoo, weekly. The only difference was CONDITIONER, while with straight hair, I don't - we also live in a city that have soft water. Many people DON'T even need, conditioner, but they do, because they are sold in stores!
YOUR HAIR IS DRY for several reasons:
1. You're using heat to style your hair.
2. You're over-blow drying your hair. 3-5 mins. is how long I blow-dry my hair.
3. You've got chemicals on your hair.
4. Your hair is naturally curly, or kinky. They're the most driest in all textures.
5. You're using products, that fixes, damaged hair. REMEMBER: No hair products can change the biology of your hair! They are not made of glue to fix, repair, make your hair grow. The hair is DEAD. No matter what the commercials says.