for some strange reason, I've though about this a lot, not so much recently, but I did for a while. I've come up with many theories/hypothesis, I've disproven quite a few, but I think I'm getting better.
You need to get right down into what is happening at the cutter/metal interface. With a conventional cut you are going thin chip to thick. The cutter begins touching the metal parallel with it, so first its rubbing, then the cutter deflects because the cutting edge of the flute has not been able to dig into the material yet, which causes even more rubbing. Then finally, it will dig in and then pull into the cut. So you are really beating the crap out of the outside of your endmill, causing a lot of additional heat, and it seems to leave a whole heck of a lot of burrs. Its basically the same thing as running far too small of chipload on a climb cut, you are rubbing and burning up the outside of your cutter, slowing turning the geometry into that of a drill.
With a climb cut, you are slamming the cutting edge straight down into the material. You aren't going to rub, you aren't going to create extra heat. Sure you are slamming into the material, but how else are you going to cut it? You can either rub it off or cut it off, I'll cut it off.
I'm sure I'm not the only one that has ever played with an axe, When I was 12,13,14 me and my buddy built a 12'X12' log cabin, 7 foot tall, never got a roof on it, but it kept us out of trouble and it was fun. Smack the axe straight down into the wood at a 90 degree angle, and it goes right in. Come at it at a shallow angle, to take off the bark or whatever and the axe would skip right off. Pretty much the same thing just on a different scale, different materials and a different cutting tool.
I hope that made sense?