No, shampoo is not the only thing that properly washes hair. Some alternatives include:
1. Apple Cider Vinegar: Its many benefits for the hair include detangling it, balancing its pH balance, and sealing cuticles. For this method, simply take an old shampoo bottle and fill it with half apple cider vinegar, half water. 
2: Baking Soda: This is a method people have used for a long time to wash hair. In addition to clarifying hair from chemical buildup, it has a weak akaline, so you do not have to worry about damage. Simply add one tablespoon of baking soda to one cup of water and use it to wash your hair! 
3. Eggs: This method may sound rather nasty, but it truly does the job. It leaves hair both smooth and shiny. Simply break an egg open, whisk it and pout over your head. Leave it on for a few minutes and wash it out thoroughly with cool water. 
4. Tea: Very common in Asian countries, different teas give different results for your hair. For instance, chamomile gives your hair extra softness. Simply massage the tea in your hair; that's all. 
5. Lemon: Its antibacterial properties have a number of advantages as a shampoo alternative. It is even used for those wanting to lighten their hair color! All you need to do is squeeze a lemon over your head, massage it in, and wash off after about 5 minutes.