It facilitates finding fellow-travelers and allying with them. There will always be parties where there is serious collective effort to influence the policy of government.

Besides, you cannot shut down political parties. They are an expression of freedom of association. It would be like trying to shut down the Lion's Club or Rotary International, because you "don't understand the need for benevolent associations at all." Same thing with labor unions.

The flip side of being an individual is the right to form voluntary associations with others. Humanness (mutual aid) is a quality of a society, not of individuals.