The value proposition for expert systems is simple. Capture the knowledge and reasoning from subject matter experts in a given domain and make it available to non-expert users through a technology-based system.
Dealing with an expert system isn’t the same as dealing with a human expert. Computers have no common sense. They are only capable of doing what they are programmed to do, and nothing more.
But there are different types of scarcity when it comes to human experts. There aren’t enough experts to help every person, every time they need help. Most non-experts won’t be able to easily afford the services of a human expert. Human experts don’t work 24/7.
Expert systems don’t get bored. They don’t get distracted. Their knowledge bases can be populated by a multiplicity of experts in one or more disciplines that apply to a given domain. Depending on the technology, a single expert system can serve high numbers of expert users at the same time.