Because they are two different things. A subscription gives you a website built on a tried-and-tested system: it costs little because the provider does it a hundred times. An agency project starts from your requirements and solves them one by one, and makes sense when those requirements truly exist: an e-commerce with hundreds of products, integrations with your management software, a brand to build from scratch.
The first thing you should know is that price doesn’t mean less work for you—it
actually means more: you provide the materials, you write or approve the content, and there are
briefs, meetings, and rounds of revisions to go through. And once the project is delivered, the website
stays as is: it only changes if you remember to request a modification, which in many cases is
subject to a separate quote. For a showcase website for a local business, those requirements usually don’t
apply, and that kind of work isn’t worth it.