Without announcing lynches, the game because 100% a guessing game.
I prefer no reveal on Night kills, for several reasons. First, if you think someone is on to you because he or she has information against you, you can kill that person and not be walked to the gallows immediately the next Day. Second, it gives hosts the opportunity to include resurrection polls and mechanics of the like, in which people have to take a risk in choosing someone to bring back. Third, it makes a lot of sense in games with more than one Mafia faction: If there is one mafia faction, then when someone is killed, you know the person who died was (almost certainly) good. With more than one Mafia, the teams can kill one another off. Fourth, not revealing a Night kill keeps the Mafia guessing if they took out a powerful role or not. As a long time evildoer, one of the things I love is trying to work out which civilians are which roles and taking out the ones we deem to be the most powerful.
If lynches weren't revealed, then civilians would never know if they made a good choice and could never determine who was genuine in their votes and who wasn't. In summary, you wouldn't have a game at all.