Hi this is Eric from Puter's team. I'd like to clarify the use-cases a bit. Puter is not meant to replace VMs but we do have support for compiled executables to run under v86 (a WASM-compiled x86 emulator). Puter's filesystem is stored on the device running Puter, and has a permission system for sharing files/directories between users. I'm pushing for a "mountpoints" feature to be added which would enable mapping a local filesystem directly to Puter (currently Puter stores its files in a flat structure which is fine if you're only accessing the files from Puter, but is inconvenient if you also wish to access them from the host).
I would say the primary use-case is that if you build an app on Puter it can be accessed on any device with a browser. The app itself doesn't need any backend code or deployment infrastructure; that's what Puter does. So, the incentive is easier to see from the perspective of a developer rather than a user.
Hope this helps. I know this thread is pretty old but if it's in search results anyway I figured it wont hurt to contribute additional information.