The metal underneath the roof rack feet usually has some rust developing. Also, the stock roof rack is fairly useless with heavy items (e.g. boats, bikes, tires, etc.). I prefer the cleaner look, as well.
Gotcha. I'd better take a closer look at mine. I was hoping I could just leave the OEM rack on when I installed a taller aftermarket one, but I'll check for signs of rust first. Thanks!