When tap water is not readily available, an eyewash like this is required under first aid regulations. Even when tap water is accessible, eyewash is often safer and more convenient since it eliminates the potential for contamination from chlorine or other irritant chemicals. 

Using eyewash removes the physical challenge of placing your eye under the tap, ensuring a more effective and comfortable experience. The solution is carefully balanced to prevent any irritation when absorbed into the body. Remember, taking quick and appropriate action with sterile eyewash can make a significant difference in protecting your eyes from harm.