This is an interesting thread, just joined in and glad to learn this as well. It's kind of a gross comparison, but it's the same reason we have earwax - it's there to protect your ear canals. However, unlike an engine, you should probably keep that cleaned up once in a while
One thing I wish they did have here in Canada is air dryers at the wash stations for winter washing. The coin-ops are a great place to clean off the salt after a week's worth of driving, but on a cold January day the water freezes and jams everything up. If they had like a leaf blower on an arm, it'd be great.