Why modern democracy cannot exist without the political parties?

Democracy could exist without political parties. Parties, in many schools of political theory, serve as coordinating institutions where individuals with common interests work in a group to attain their ends more readily than by themselves. Parties are useful because they allow for common control and operation of democratic institutions, but democracy could operate without them. For example, in many countries, elections (where at the municipal, sub-federal, or federal level) don't allow candidates to be affiliated with any particular political party.