Even if it costs less in the long run, increasing their startup costs might decrease growth enough to make it now worth it. And since they demand uniformity everywhere, they'd be in the position of imposing change on their existing franchisers who might not want it, which is never fun.
Definitely not true. I worked for a corporate store during high school, and only later in College moved to a franchise for a year. At my corp store, we were one of the first stores in the country to move to the batch cooking method (with microwaves no less!), as well as the speakerless drive through (take orders directly at the window). None of those was replicated at the franchise I worked for later.
Even if it costs less in the long run, increasing their startup costs might decrease growth enough to make it now worth it. And since they demand uniformity everywhere, they'd be in the position of imposing change on their existing franchisers who might not want it, which is never fun.