I suppose I just don't get what they are going for.
I guess it's an acquired taste, but there's something fun about trying to survive in such a hostile world. How many game servers have 200+ page comics written about them? http://minecraft2b2t.thecomicseries.com/
Someone can approach you from 200m high building a 1m-wide bridge from outside your radar and just drop lava (or active TNT) on you. In minecraft, you need a pretty high defender:griefer ratio to keep things intact.
http://minecraft2b2t.thecomicseries.com/comics/104/
EDIT: Looks like I've gotten sucked in again. Feel free to message me if you want to try.
Then there's loads of other plugins that people use to find ore, hidden buildings, track players, speedboost, fly even on servers that disallow it, etc... etc...
I wanted to like Minecraft. The hilariously insecure gameplay is what breaks it. It's not a game of survival, it's a game of trolls who can exploit the most.
On the other hand, when almost everyone is using those cheats, it levels the playing field a bit.