While what you say was true about Vista, in Windows 7, 8, 8.1, and 10 UAC prompts are suppressed when they're the direct result of user interactions within the OS itself. Each OS reduced the number of UAC prompts a user experiences.
They also broke the security on the default configuration because now you can just interact with the system components to bypass UAC, see e.g. [0]. This is officially not a security vulnerability because UAC isn't actually a security barrier unless you set it to "Always prompt", but just a feature to make applications play nice. But note that it's not on "Always prompt" by default...
