In single-party states like the former eastern bloc (Soviet Union, East Germany, ...), there is only one dominant party. One thing that has always bothered me is that this is a contradiction in itself: a party is a part of the whole, it is by definition partisan or partial. If there is one organisation for everybody, then it is no longer a faction or a party, it is just an institution of the society.
Why do they bother keeping around the legal "machinery" for having multiple parties, when the ideology or even the constitution of the country says that other parties can't be registered (or are marginalized)? Wouldn't it make more sense to say, OK, we won the revolution, now we merge the party with the state? Or we rename it to, say, "politicians guild": Everybody who wants to take part in politics joins the official guild, and then you just ban all political parties and factions altogether?
This question is distinct from Why do one party states hold elections? , as you can have elections in a one-party state, and you can have elections without parties. I'm not so much interested in why there is sometimes a charade of elections, but rather why they keep the paradoxical "fraction that represents all". Is it e.g. for tradition, or is the party thought of not as universal, but as a fraction against the class enemy, etc.. A justification from the communists / socialists themselves would be most interesting.