So that more people can have a chance to get a house. If a plot is becoming free at midnight, and that the timer duration is 8-12h max, you exclude from the sale all players reconnecting the next evening in peak hours.

And the lottery is not gonna be as fabulous as you think. People are already getting angry not getting their drops against 7 other players in an instance spammable every 10 minutes. Now imagine it with hundreds of players to compete against, and having to wait several days between each try the rare times a plot become available again XD