Why do people still play Minecraft classic/host classic servers?

MC Classic is very very old, but people still play it and even host multiplayer servers for it. And there's nothing wrong with this, but i'm just wondering why.
Is it because it's free?
For the nostalgia?

Well first off, yea, because it's free. Plus, without having premium, it allows for different mini-games to be played. Normal classic is purely a restricted creative mode (meaning a few objects rather than all objects in premium). I was a mod, admin, and owner of a few MCDawn and MCForge servers. Lots of fun.