You're confusing fact with fantasy. WDW and Main Street USA are not fact; they are fantasy. Main Street USA is located in Orlando, Florida but we want to pretend it's Small Town USA, never mind that Small Town USA never looked like that. We want to pretend that it's 1906, never mind that it's 2012.
WDW or Main Street USA is not intended to be authentic. It's intended to be our preconceived notions of what was authentic for circa 1900 with the modern conveniences added it. Nobody wants to go to the bathroom in an outhouse. Subconsciously, we accept running water and a flush toilet because we think circa 1900 Small Town USA was perfect and, therefore, accept that they had toilets that flush even if they didn't.
The same is true for any product that appears on Main Street USA. If it fits into our preconceived notion of what's "right" for Small Town USA circa 1900 then we accept it. If it doesn't, then we reject it. Starbucks is a modern brand. It is difficult to imagine Walt Disney drinking Starbucks even though he undoubtedly drank coffee. If it were Maxwell House (founded in 1892) being put on Main Street USA, then people might accept it more than Starbucks (1971). It's not something we're consciously doing. It's subliminal.
Walt Disney World is exactly that, Walt Disney's World. More specifically, it's our view of what was or at least should be Walt's world. If we, as consumers, can connect a product or technology subconsciously with Walt, then we accept it. Walt certainly never lived in a place like Tomorrowland but he dreamed about such a place. So, if something, anything, matches our idealized view of what we think Walt liked, we like it as well. It doesn't matter if Walt liked it. It doesn't matter if it existed when Walt was alive. What matters is, in our heads, we think Walt would have liked it.
Starbucks caused an uproar in part because it's the modern world interfering with our idealized view of Main Street USA. Main Street USA is run by one of the largest companies in the world but we like to pretend that it's run by our friendly next door neighbors Chuck and Vera. It's an illusion and it's important that WDW maintain the illusion.