This is second hand, so I don't know if this is true as it occurred before my time.
Years ago, a number of shops tried to organize to cooperate to promote diving, as (guess here) they realized that slagging each other just drove people to other sports. While the weather sucks in Seattle, there are a lot of outdoor activities to do. Diving is year round of course, but winter there is skiing/snowboarding/cross country/snow shoeing. Year round: biking, hiking, backpacking (if year round, road & trails. Spring/summer/fall: swimming, waterskiing/wakeboarding, hiking, backpacking.
There is always something to do outdoors if you are dressed for it to deal with inclement weather.
It is these other sports/activities that is the biggest competition/threat to diving.
Sadly, a shop chain allegedly complained (to the state AG?) about anti trust or something, which killed it.