Tiles does it too, it just depends on the container and probably your perception, like i2amroy said already.
I’ve noticed that a lot of people don’t realize that. I’ve seen on Youtube, a few different people, just walk into a room and hit (V)iew, not realizing they can only see the top item of the stack, even after finding other items in said stacks/conatiners.
Azrad explained it to me a while back in http://smf.cataclysmdda.com/index.php?topic=14493.msg299746#msg299746 a while back and I think it all still applies, if your interested in taking a look.
I believe you can seal crates up with items in them, as well, and maybe coffins now too(at least with people in the coffins, not sure about other items).