What do you get when hot smoke hits cold metal? Condensation. Not good.
If I understand correctly the idea of the mesh is to keep tobacco bits from blocking the draft hole. It is a problem alright, but there are some tricks you can use to reduce it. Large pieces of tobacco are usually not the problem, it's those little tiny ones that tend to do the blocking. I make it a habit when loading my pipe to use the larger bits at first, then the smaller bits on the top. If the tobacco is loose like in a jar a little shaking will cause the large ones to come to the top and the small ones settle to the bottom. When the jar is full or near full I just use the large bits. But when it starts getting to the bottom that's when I start the separating. Load some large bits the give the jar a few more shakes and... here's the trick. Tilt the jar away from you about 45 degrees, give it a couple of shakes. Now gently tilt it toward you until the tobacco falls over to you and at the top of the pile you should see the small bits of tobacco. Using my index finger and thumb I pick some and top off the pipe. I know, kind of hard to explain.
Not only are there now no small bits in the bottom of the bowl to block the draft hole, but the small bits at the top make the pipe easier to light too. That's it.