For whatever reason, the only time I see people de-register is after a heated argument when everyone is upset. I think if we are to have it in place, it needs to have harsh consequences merely so people won't use it to prove a point.
Maybe that's just me though. I don't care either way honestly. If I leave the game, I doubt I will de-register. I'll just disappear into the sunset.
Sometimes people de-register because they just need a break and I really don't think they should be punished with year-long banishment for that.