Jehovah’s Witnesses at SeaTac Airport

I travel a lot domestically and internationally, and don’t generally see a lot of religious affiliated soliciting at airports. Every time I’ve gone to the SeaTac airport there have always been a group of Jehovah’s Witnesses standing at the exits passing out literature. Granted, they are peaceful and non-disruptive, but it seems kind of weird I guess?

I assume there must be permitting of some kind involved to do that sort of thing at the airport, but it seems strange that an airport would allow for that and why don’t we ever see any other religious groups doing the same thing at SeaTac? I’m sure other faith-based groups would be interested in doing the same thing but it seems there is a preference for only Jehovah’s Witnesses at SeaTac?