The reason that it’s generally easy to steal tires is that the tools to remove lug nuts is common to every vehicle. In theory, anyone with a jack and the correct socket wrench can make off with your tires. Wheel locks require a key that is specific to those locks, so they make it much more difficult to steal.
And while the locks themselves are not 100% theft-proof, that difficulty itself is an effective deterrent. Often, thieves tend to go after easier targets. The faster a thief can get your wheels and leave, the more likely it is that the thief will take a shot at them. A tire lock makes your vehicle a more difficult (if not impossible) target. That alone will deter many thieves from even attempting to steal your wheels.