The short version is that while many users can differentiate, it's more a problem of WHEN they differentiate - Chrome's entire design philosophy was around speed, and the omnibox was designed so that we had a simple destination that a user could focus on when they had decided to go somewhere else, but before they had decided WHERE they wanted to go to or HOW they were going to get there, and then make it so they wouldn't have to think about the HOW. If their search term autocompleted to a URL so they don't have to go through search, that was a win. This same philosophy was what drove putting the most visited pages on the New Tab Page (which was a blank page in most browsers at the time).
Some users plan out their actions before they take them, but I wanted to make everything as streamlined as possible so you could interact with Chrome as you thought about what you wanted, and not making you wait until after.
[1] I was the designer and occasional engineer, but the entire team takes the credit - everyone was behind the idea from before we even started work on Chrome, and many smart people deserve more credit than I do for how good it ended up being.