Have you ever played chess? What would happen if the black knight suddenly started moving straight rather than two and a half squares? Or, what would happen if in a game of cricket, there were no umpires? In any sport, we need to follow certain rules.
Change the rules and the outcome of the game would be very different. Similarly a game needs an impartial umpire whose decision is accepted by all the players. The rules and the umpire have to be agreed upon before we begin to play a game. What is true of a game is also true of elections.
There are different rules or systems of conducting elections. The outcome of the election depends on the rules we have adopted. We need some machinery to conduct the elections in an impartial manner.
Since these two decisions need to be taken before the game of electoral politics can begin, these cannot be left to any government. That is why these basic decisions about elections are written down in the constitution of a democratic country.