Actually, for backwards compatibility, while being able to move forward and only having to maintain a single code base.
It is a kind of legacy situation. We have multiple projects which depend on different versions of a socket.io plugin. They targets socket io protocol v2, v3, and v4. Each has its own quirks and bugs. And there is no easy path to up- or downgrade those plugins to a single version.
My hope is, to have a minimal implementation of the socket.io protocol (or the various versions) which just suffices to provide those apps with what they need. And they only use a very tiny part of socket.io features.
