I want to say that when a server has 18% population (based on it's set size) it auto kicks idle players after 300 seconds. Prior to that it does not and this is so they can help try to seed it.
Pro's and cons exist for doing this of course but like you say, people will play if it's running. If it's not and no one is starting it, AFK is how we try to start it. I do this a lot to try to help start the US server because I am working and can't really play but the "hope" is that my filled slot will help start it and once it's going I drop out or get kicked if I forget too.
That said, ideally we don't have a large number of idle people like 5+. I agree though that you shouldn't have to get suckered in to be the only true alive player but that's really when you can type in chat and ask if someone on the other team can switch or poke an admin to switch someone for you to try to balance it out.
Basically we all hear you and it's not a new talk we're just trying to balance those pro/con of it. What you describe can become the con if not careful.
When I am AFK I try to keep an eye and if I see I make it unbalanced I move myself to the other team so it will auto balance another player.
Hopefully this all helps you understand. We're open to suggestions if you have some as well.