My interest in Gmod died out when old ZS became less frequented. I know it was inevitable and uncontrollable, but that long downtime the servers had really bruised what player base we had. When the fun people I got to know stopped playing on the servers, well it just wasn't the same for me anymore, and I moved on to playing other games.
I am not one to hop servers either, so I couldn't find it in myself to play on another server. For me it was random or nothing, still is. I still come on the forums and check out everything, because this is still my community, but gmod just really lost its flavor. I'd say if the same people from then were still playing, I probably would be too.