When developing software systems, knowledge of a domain (possibly many) is required to come up with the requirements of that system. often times, It's very hard to gather these domain requirements, and requires someone who's delved in the domain. This is especially problematic for a single person or a technical-only team.
Of course, technical people who develop such software systems try to learn about the domain. For example, they Google about the topic, go to Statista to read research made in the domain, and they might even talk to (or hire) domain experts about the system they are developing. However, this is not always feasible due to time, cost and/or nature of domains.
Personally, this problem occurred to me when brewing up an E-Commerce SaaS idea. I looked at other players in this field: Shopify, WordPress. etc. and I found it very hard to find to find the domain problems of E-Commerce as someone who has 0 domain experience.
Finally, this problem affects all domains and sub-domains. Here is a list of industries (domains) published by BLS