Ever wonder why golf balls has dimples? It's there for a reason, and the reason is to reduce air resistance. When air travels over a polished surface at high speed, it tends to stick to the surface and create a lot of air resistance.

In the case of cylinder ports, the fuel will stick to the polished surface and separate from the air mixture, which is a very bad thing. Port and polish is just a saying back in the old days, nowaday no one polishes the ports anymore. You can polish the exhaust ports, but carbon will builds up over the surface very quickly. Hope that helps.