Pepsi v. Coke: and the winner is...Dr Pepper

Here's an exchange I've had several dozen times.

Me: "What would you like to drink?"
Customer: "Coke."
Me: "Pepsi okay?"
Customer: "Dr Pepper."

I don't get it!

Okay, I'll admit I grew up in a different part of the country (north of the Mason-Dixon line), and the difference between Pepsi and Coke is negligible to me. Sure, in a side-by-side test, I can taste the sweeter Coke (but prefer Pepsi). But to have such loyalty to a soda? They are almost indistinguishable. Dr Pepper is the outlier.

Now, I can understand loyalty to a regional soda, such as Nehi or Royal Crown or even the old cream sodas, but Pepsi and Coke are international megabrands. An entire movie set in the Kalahari Desert, The Gods Must be Crazy, was built around an old-fashioned Coke bottle. Coca-Cola delivery trucks rumble through the deepest jungles of central America. Siberians know what Coke is. I've seen the logo in Hindi and Arabic.

Brand loyalty is a testament to the marketing skills of these two giants. Taking it one step lower: how is it that perfectly intelligent adults are willing—desperate even in some cases—to go to great inconvenience to pay outrageous prices for water with corn syrup, flavoring, and carbonation? And to claim slavish loyalty to "their" beverage?

Again, I don't get it.