Firstly, democracy means the colossal number of people vote to appropriate parties. Further, from each party, a leader get selected this leader then votes for another leader who is appropriate for President's position. Compulsory voting is the right of every individual to elect the person of their choice.
Secondly, if we consider one country to illustrate, India, where voting is not made compulsory since many people will not be aware of what changes are made to the growth of nation also people will be bound by rules and regulations