Auto Designers: Your Help Please

This is a question that has intrigued me for some time: why do car radios sometimes have identical dials for 'volume' and for 'tuning'. I find this a little frustrating. I've seen this more than once, so I'm guessing it's a design decision for some reason like the following:
a) It's pretty to have knobs the same
b) It's cheaper to manufacture identical parts
c) It encourages drivers to use the steering wheel controls
d) Who cares—it's not that hard to learn

What do you think?

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