That's why credentials, furniture, street address, references and "experience" become proxies for value and competence where an intangible product is concerned. Even tangible products such as fashion items or vacation resorts have a huge and similar problem, namely creating a brand or mystique that helps potential buyers evaluate the product, which either is a means to another end, or an "experience."
Those are reasons why content marketing can be effective. Content marketing can help establish credentials, provide evidence of experience and knowledge and thereby reduce the "risk" a prospect faces when buying an intangible product they might not ever have used before, or which gets used infrequently.
By creating great, valuable content you are setting up your brand as a trusted expert, someone your target audience can count on. They learn that your company is one of the real experts in your industry. This helps builds your authority and trust level. Those are proxies for the product attributes potential buyers otherwise evaluate directly, in the case of tangible goods.