A lot of the people in my close circle of friends and coworkers have iPhones, but almost a year after it came out I'm still the ONLY person I know of that has a 5S. My wife and one or two friends have 5C's, a few people have the 5, and the rest seem to have the 4S still. I'm baffled that I have yet to see a single other 5S in the wild with my own eyes.
Unless you're in an urban center seeing people on the bus everyday or happen to live in a high income area chances are most people in your area are more budget oriented and either run an older phone for longer, or upgrade to the less expensive models. Most people around here will go with whichever model is free on a contract at the time and don't care that their phone might only see one more fully functional iOS update.
I'm also the only person I know with a 32GB iPhone, my local Telus store doesn't even get anything higher than 16GB in for inventory because they very rarely sell the larger capacities. You have to special order 32GB and up to get one at a carrier around here.
One of the guys I work with plans to buy the biggest screen and capacity iPhone 6 available when they come out and that's unheard of around here.
I guess the moral of my story is cost is the biggest actor to a HUGE majority of iPhone buyers. I'll have to ask my buddy at Telus what he figures the ratio of 5S-to-5C sales would be at his store as I'm curious to know now. I'm willing to bet 5C/4S still outsells the 5S around here by a large margin.