Serverless functions, right? That's what deno deploy is billed as. Presumably the registry is a platform-adjacent investment to try and bring more serverless market-share to deno. Since it provides a npm-registry compatible facade, presumably you should feel safe publishing deno-y code to it (without calling platform APIs?), and should thus be more likely to use deno, and thus enter the funnel for deno deploy.
Personally, I just use deno's rust v8 wrappers a bunch, since they make embedding a V8 runtime into a rust app very simple, and js is a very nice scripting engine (especially with optional types). A hugely valuable contribution to the open source community. But then again, I don't deploy serverless functions on the regular. To each their own.