Jehovah’s Witnesses maintain "do not call" lists. It's a list of addresses where the householder has expressly asked for them to not be disturbed.
When Witnesses gather and plan out exactly how they're all going to go door to door on a particular day, one required task is to check this list, and to do their best not to call on any houses on it.
It's easy to be added on the list; you just need to ask. "I want you to never call here again. Please put me on your 'do not call' list".
When someone asks like this, Witnesses are taught to do as asked. And they are also taught to honor any do-not-calls.
Unfortunately, this doesn't mean they'll never call again. As they will once a year due to their justification that you may have moved, or had a change of heart. Also they sometimes make mistakes. Which can actually be hilarious because if they realize after they've knocked once or are part way to the door, you'll likely see them sprint away hoping they aren't seen.
Now, I'm sure many of you don't have to deal with Witnesses that often and are wondering why this would be necessary.
There aren't that many Witnesses globally. About 8 million now. Some towns have many times more witnesses than other towns.
A specific congregation is tasked with hitting every street in their assigned territory once every six months or so. But if the congregation is large, and has a relatively smaller chunk of area to work, this could be much more frequent. Basically, a street is worked, and then the card representing that street is moved to the bottom of the stack of territory cards, until all the other territory cards are also worked and that first street's card makes its way to the top of the pile again.
Also, when witnesses work a street, they will work it up to three times. Each time taking note of "not at homes", in order to specifically try these houses again the next time (probably next week). The goal is to get everyone on the street. So if you are hiding from them, you may have them knock on your door three times in a very short span. And then, if you're in a heavily-witness-populated area, have them return a couple months later.
Other areas might be far far too large for the congregations to work like this, and as such you only see them once in a while. Plus, if you're actually not home when they come around, they may appear even more rare.