Built for the case a chatbot handles badly: five people producing copy that all has to sound like one company. Jasper holds your brand voice, style rules and product facts centrally, then applies them across campaigns, landing pages, ads and email, with templates for each and a workflow for reviewing what comes out. The output quality is comparable to a frontier model because it is largely built on them; what you pay for is the scaffolding.
For an individual writer that scaffolding is overhead, and the price is hard to justify against a $20 assistant. The moment it starts making sense is when consistency across people matters more than the quality of any single piece, which is to say when you are a marketing team rather than a marketer.