Years ago they used CB frequencies.
If someone were blocking the use of those frequencies in the name of security they could easily screw up those openers.
A number of my friends and I were in the vanguard of CB ownership in the early to mid-60's. I have to admit to getting drunk and on a few occasion opening and shutting my neighbors doors.
It didn't take long for the companies to switch to a two-tone system, which was almost impossible to figure out and the whole idea lost it's appeal.