The Snap client is hard-coded to use Canonical's Snap Store server, so not only would the developer have to reimplement the server, they would also need to fork

The Snap client is hard-coded to use Canonical's Snap Store server, so not only would the developer have to reimplement the server, they would also need to fork the Snap client to support alternative servers. Anyone who wants to use an alternative server would have to install the fork instead of using the Snap client bundled with Ubuntu. Considering this additional obstacle, it would be much easier to stop using Snap and switch to a package manager that supports multiple servers or repos in the first place.