It's just incredible how people who are seeing pictures and lack the imagination to understand what purpose they serve then assume it must be no real purpose and that the folks who are doing it are just absolute morons.

Perhaps it's not there for when you're out and about and actively being seen by the enemy. Perhaps it's there for when you're hiding in the woods and you want to hold a tarp off of the top of your tank so that you can get in and out easily. Perhaps it's there to hold up camo netting for hiding the tank better while stopped in the woods. Perhaps the mesh on top is to hold up branches that you cut down to try and better hide your tank while you're in the woods, not moving.

I'm not saying that any of these reasons are THE reason. I'm suggesting that if some idiot on the internet (me) can come up with some reasons that aren't entirely moronic it's too bad that better informed folks aren't trying a little harder to imagine what they might be used for.