Should your shampoo have jojoba?
Nevertheless, you have less choice than you might think.
Removing the oil
Technically, you can cleanse you hair with bar soap, but it would leave a dull film. So shampoos all contain one or more detergents instead--chemicals similar to soap but less likely to leave residues. Known as surfactant, the detergent bonds with oil and dirt and washes them away. Shampoos for oily hair may have more or stronger detergents. Most shampoos also have a foam booster, added because people associate suds with cleanliness. By the way, despite the ads, there's no such thing as a "self-adjusting" shampoo.
Putting it back
Because detergent remove the oil, most shampoos contain conditioner (lanolin derivatives, balsam, glycerol, propylene glycol, and various oils) to replace what's being washed away. These can fill in the cracks in the hair shaft, make it shinier and better looking--give it "good handle," as cosmetic manufacturers say. A separate conditioner produces ever better "handle," since more of the conditioning agents may stay on you hair.
Some shampoos contain proteins (keratin, collagen) that are supposed to stick to hair and make it look fuller. Botanicals such as mint, chamomile, or other "natural" or herbal ingredients may be added, presumably to boost luster, though they mostly just boost the price. All this stuff goes down the drain when you rinse.
Other ubiquitous shampoo ingredients are the scents, thickeners, and colors that are added to make the product itself more attractive, plus the preservatives that keep it free of bacteria.
Anti-dandruff shampoos are big sellers, and frequent shampooing with one of these (or even an ordinary shampoo) is generally effective at getting rid of dandruff. The active ingredient is usually pyrithione zinc, selenium sulfide, a sulfur-salicylic compound, or coal tar--all considered safe and effective by the FDA. Everybody has a little dandruff, as it's natural for the skin to shed its outer layers. If your dandruff is severe and causes crusting, itching, and redness, consult a dermatologist.
The pH balancing act
Most shampoos are very slightly alkaline, so citric acid or another ingredient may be added to achieve a more balanced pH (closer to neutral). This sounds reassuring, but probably makes little or no difference to the look of your hair.
Less may be more
What you wash your hair with is seldom a health issue (unless you have a scalp disease or are allergic to some ingredient). No shampoo can "nourish" your hair or make it healthy. The hair shaft is dead tissue, and if has been split or roughened, the only real cure is to cut the damaged parts off. Shampoo prices vary widely and are no index of cleaning ability or consumer satisfaction. In blind tests, most people can't tell one product from another. You might try using smaller amounts of shampoo or diluting what you use--if often works as well. And there's no law saying that you have to lather up twice in order to get clean.