This is all due to poor mission scripting.

BIS has already got a Garbage collector module built into the game, all the scripters need to do is use it. OR better yet, make their own!

This is no fault of BIS, again, it's poor mission script quality.

Mission makers should add a repeating trigger with this:

{ if (!alive _x) then { deletevehicle _x } } foreach (nearestObjects [player, ["Man"], 200]);

So that all bodies will get deleted when ever the trigger fires. (set range to whatever you want).

I am not sure if the garbage module in the editor is working, never got it to work in A2 at least.

^ another way is to put 'killed' event handlers on every 'man' when they spawn.

The eventhandler script can just have "sleep 10; deletevehicle _this select 0;"

http://community.bistudio.com/wiki/addEventHandler

Alright thanks guys. Look's like this issue is solved then due to my poor researching and poor mission scripting. Thanks guys.

As others pointed out, this is due to poor mission scripting, not a game issue.