>> regular users CAN NOT turn off UAC.
Again, yes they absolutely can. how?: Install windows or even buy a new laptop with windows. First reboot after setup it comes straight up into a desktop, turn UAC off. simple.
Your concept of a distinction between regular user and admin user is understood, but not what people get outside of a corporate environment where an IT dept sets up users accounts, unless they know enough to manually do it themselves.
My usage of the phrase "regular user" means the default account everyone gets on their Windows PC when they buy one.
The notion of windows security is ridiculous as long as Microsoft keep making the default account of a PC have admin rights, as most home users don't know or even care enough to limit their own rights preemptively. They just buy the laptop and for the life of it use whatever desktop comes up when they power it up, and from there, they absolutely can and will turn off UAC.