At Costco, they're less "greeters" and more "people who check your membership card". Actually, since Costco switched to automatic card scanners, they're "people who watch to make sure you scan your card and the machine makes the happy beep".
That said, at least at my local Costco, they also smile and welcome you into the store -- it's just not their primary function.
As popcornpizza called out, most of the answers in this thread unfortunately seem unrelated to your question.
I live in the US and haven't been to the UK in years, but I do visit Romania every year or two. I don't notice a big difference between Coke Zero sold in the US versus Romania. I'm certainly not a Coke Zero expert, but they taste pretty much the same to me. My hunch is that Coke Zero tastes the same across Europe, but I'm happy to be corrected.