This is horrible and I hope it doesn't encourage anyone to do this. No friendships beyond the very shallow relationships you can develop with the workers onboard the train or the people passing through.
This feels inhumane to me. I can't imagine someone being happy doing this for any length of time.
I don't see why this would prevent friendships. You don't have to be on the train 24 hours a day - just overnight while sleeping. If you have friends in Berlin you can arrive in Berlin in the morning, spend the day hanging out with them, then head back to the station at 10pm for a night train to somewhere else.
At its best this could enable you to maintain friendship groups in multiple cities.
This is kind of what I want to do for several years with my girlfriend. Hide out from the real world on the trains of Europe and explore. Can someone tell me if this pass is Germany only or is something like this available for a lot of Europe?
It's Germany only, but Germany is pretty big. As a foreigner not sure if you'd be able to stay that long without applying for a visa, and you won't get that without a permanent address. If you know someone there you can maybe register at their address.
edit: but for the whole of Europe you do have Interrail but not sure how much it costs. I doubt you can do that every day but could be wrong.
This feels inhumane to me. I can't imagine someone being happy doing this for any length of time.