WordPress meets Git, properly. Undo anything (including database changes), clone & merge your sites, maintain efficient backups, all with unmatched simplicity.
Possibly the best thing about WordPress is how simple it makes most things. Just a couple of clicks and there you have new plugin installed, a shiny theme activated, that annoying user deleted, and so on. People love this, and we do too.
There's a flip side to it, however. Most actions are irreversible and done straight on the live site, which is dangerous. What if a plugin had a bug? What if you your client did something stupid? These things happen and are unpleasant to deal with.