We used NextJS on a project hosted on AWS a while ago. We learned quickly it wasn't the best tool for what we wanted to do which is why we stopped using it. But it's an open source project whose purpose is to drive devs to Vercel. It doesn't surprise me that there are some features that work best with Vercel (but it does surprise me that only recently other providers started to need adapters).
Anyway, my point is that no one is forced to use NextJS and if they like NextJS but not Vercel they can always fork it or, apparently write an adapter.
Besides the way it maps server side code into serverless, it has a custom runtime, functions that expose cloud infrastructure, integration with multiple language runtimes for the backend.
You get to pick Vercel + headless CMS + assets managed + eshop, and you're done in terms of big corporations.
Might seem a lot in licenses, however it allows for smaller dev teams, which is what management floor cares about, all those salaries.