Binary comparability extends beyond the vide that runs in your process. These days a lot of functionality occurs by way of IPC which has a variety of wire protocols depending on the interface. For instance there is dbus, Wayland protocols, varlink, etc. Both the wire protocol, and the APIs built on top need to retain backwards comparability to ensure Binary compatibility. Otherwise you're not going to be able to run on various different Linux based platforms arbitrarily. And unlike the kernel, these userspace surfaces do not take backwards compatibility nearly as important. It's also much more difficult to target a subset of these APIs that are available on systems that are only 5 years old. I would argue API endpoints on the web have less risk here (although those break all the time as well)