Why is looting your teammate a thing…

I entered trios with 2 randoms in Outpost, and everyone did well, everyone was gaming and killing till we reached the pinwheel and looted everything (everyone was generous to the other, nobody was selfish since we were asking before taking)

But in the end…we were fighting the 3 red card door room, and i got downed from UESC (there were 3 min left on the clock), and guess what, they waited till i died and looted my body…

I pretty much lost everything valuable to me….being kind and sharing with randoms basicaly means nothing…

I just dont get why its allowed to loot your teammates