> Again, native me thought, "Why not have both Coke and Pepsi and let the customer decide?" I am not sure whether there was a pricing issue that prevented management from buying both—like the loss of a discount for going Coke-only or whatever.

There's a bunch of pricing stuff (typically the bottler sells syrup and rents dispensers and may supply drinkware, and you get discounts on everything when you buy more syrup, and you get advertising subsidies when you put the brand logo in your ad, etc), but there's also logistics. More options means a bigger soda fountain and probably more space storing syrup.

I'm not sure I've ever seen mixed brands in a single dispenser (other than 7up+DrPepper which is bottled regionally by Coke bottlers in some regions and Pepsi bottlers in others; so you might see Coke with 7up and DrPepper or with Sprite and MrPibb). But, rarely, I've seen dispensers from both. Mostly at convenience stores and also the Yahoo employee cafeteria at the Sunnyvale HQ on First Ave (which they left some time ago). Some restaurants that don't have a fountain will stock cans from multiple brands, too.

All that said, from my life experience, very few people express a strong preference, giving customers a choice probably isn't worth the effort.