That's usually sufficient to guarantee proper operation, but not when the ionosphere is wobbling about severely. Then there are the radio-propagation games played by the troposphere, the breathable layer of the atmosphere. When it's very cold and a strong inversion develops, so that the hills are much warmer than the valleys, other local signals operating near garage-door frequencies can be bent or bounced from their path. Garage doors then can receive stray radar signals, military communications, all manner of normally unnoticed broadcasts. That's where Murphy's Law and its corollaries came in.
Garage door openers, like every other device, can go wrong.
Naturally, bitterly cold weather is when their owners would least like them to go wrong. And that, coincidentally, is when the troposphere can become unreliable. Furthermore, during our cold spell the sun turned stormy and put wobbles in the ionosphere.