That isn't true for all tents with one opening. The ones shaped like a dome have loot in them but the loot is usually clipped in the ground so you need to have your inventory window open to see it. The rectangular tents that were present in the DayZ mod that used to have loot in them, don't seem to spawn loot often if at all in the stand alone game.

There is a screenshot attached

Okay, if everyone has it, than everything is alright :)

I'm not using a launcher and I installed and started the game out of steam. there are no starting parameters.
I didn't add any script or modifications.