Why play teams/squads to be alone?

Someone please explain this to me. I’m back to playing after forced rehab. I usually play Blitz or Reload when BR seems too long.

Whatever I’m playing I notice that on teams people often run off on their own. Often to fight & die alone - sometimes repeatedly. I’m not the best player but I’m inclined to meet & load up BEFORE going to war. In Blitz I started playing on teams of 6 just to get 3-4 people that would play like a team.

Am I the weirdo here? Why do people select team & then run off by themselves? Why aren’t people naturally inclined to meet up & journey together?