User Account Control's default state is to be enabled. And for a good reason. Under normal circumstances, you'd get a prompt to confirm various actions before they can take place on your computer.

Windows displays a User Account Control (UAC) prompt whenever you attempt to install or run an existing application as an administrator. If you want additional control over your account's ...

A UAC prompt is shown, asking for permission when an application wants to make a system change like changes that affect other user accounts, modifications to Windows system files and folders ...