After you've washed your hair it natural dries out over subsequent days. To hydrated and soften the hair properly another wash is needed.
There is a belief out there that water is bad for black hair and that view is completely wrong. I had a misinformed hair stylist tell me that my scalp itched so much because I washed my hair too often - huh? Once a week is not too often at all. In fact, if I go past seven days without doing a wash my hair gets harder and harder.
To keep hair moisturised between washes: spritz it with water. Then add a leave-in conditioner to reinforce the moisture; finally, lock the moisture in using an oil and cream via the LOC or LCO method.
If water is so great, why not wash natural hair daily?
Because the washing process is a prime time for breakage.
When you're handling your hair in any way - washing, combing, styling - you will release shed hairs and get some breakage. If your hair is short breakage during washing and handling is minimal; if your hair is long it will tend to tangle more leading to higher rates of breakage during your wash.
In summary, moisture = hydration, hydration = water, hydrated hair = less breakage. If anyone tells you that water is bad for black hair get them to drop me a line to explain their science!