It has nothing to do with RF, it has to do with licensing fees from the FCC, in order to function on different frequencies. It is an expensive proposition. What many manufacturers do is offer some form of IR input as a solution. Lutron makes them, X-10 makes them and I'm sure many other companies make them.
I don't know how HomeLink is doing it, unless they are somehow paying FCC licensing fees or found a way around them. They could have also taken a blanket license of some kind, paid tons of money for a certain range, and build those fees into the car. I honestly don't know. However they are doing it, it is unlikely that remote control manufacturers will do the same thing, if they want to offer reasonably priced remotes.
Thank you,
Damon DG
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