That shampoo brand is extremely common and popular in Kuwait, kind of like Pantene in the states. So it doesn't really need to show "proof" that it works. And who says a shampoo bottle must show a picture of hair? Most shampoo you get here has no pictures on it, just the brand logo.
Well, a picture of lovely locks makes much more sense, especially as the woman is shown.
Then they could've just used a brand logo, whats' the point of showing a woman if they're absolutely not showing her hair?
What next? An advertisement for a face pack for glowing skin, showing a woman in a niqab with covered face?