Even custom cams aren't perfect

As far as the unfinished areas between the lobes, the blank is cast iron and that is just rough cast iron that you see. You pay for the r&d of the lobes, the grind, and the machining of the Cam to create a finished product.
Rough cast iron isn't necessarily pretty. Now billet is another story. Whittle a cam out of solid round stock of steele and it will be pretty. That will cost you double though !