The environment variables are not about "sessions", they are about arbitrary process trees. For example, during my regular usage, I launch dozens of scripts wit

The environment variables are not about "sessions", they are about arbitrary process trees. For example, during my regular usage, I launch dozens of scripts with slightly altered env vars (want to see time in Australia? override TZ). Build system uses env variables to pass settings around. Remote connections use them to override language settings. I think the better equivalent would be things like "current user/groups/ulimits" (which are all even more restricted than strings), or inheritable command-line.