The why is sort of at the limits of my knowledge. I can tell you a ‘close enough’ what, though.
By default, Windows tries to install programs to the program files directory, but that requires admin, which triggers user account control. However, apps that do not require admin to install or run can still be installed to the users profile. Clicking cancel from a UAC prompt will just try to install the program locally instead of for all users.
My assumption is that many system administrators believed UAC was enough, or that programs installing locally (as in, just for that user) and not requiring admin were not a big deal.
The why is sort of at the limits of my knowledge. I can tell you a ‘close enough’ what, though.
By default, Windows tries to install programs to the program files directory, but that requires admin, which triggers user account control. However, apps that do not require admin to install or run can still be installed to the users profile. Clicking cancel from a UAC prompt will just try to install the program locally instead of for all users.
My assumption is that many system administrators believed UAC was enough, or that programs installing locally (as in, just for that user) and not requiring admin were not a big deal.