When men starting eating meat it might have been necessity because human body cant make proteins from amino acids directly. Plants can utilize inorganic nitrogen and organic nitrogen sources to make their proteins. However some plants growing in marshy , humid places dont have chance to obtain their nitrogen sources in plenty so to meet deficiency of proteins in their body they catch insects and eat them . They get enough proteins directly to keep them healthy
Here is Nepenthes superba from the Justus Liebig Universitat Botanical Garden, Giessen Germany.

Are you taking your proteins regularly.