Everything you bring with you, you take back with you. This includes the bodies.
Jokes aside, it's just good manners to always leave an area cleaner than you found it. This means pick up after yourself and anything extra you find in the area.
Guess there is not enough "pack in and pack out" signs installed around the area.
Seriously though, Everest should start requiring expedition groups to bring down bodies of any of its members that drop dead. Though it may be difficult if conditions are hostile and such.
Litter is definitely a huge issue on the mountain. Individuals should bring down twice than they brought up. If you bring up a bottle you bring down two.