There's always a reason for breaking spokes. I've never broken a spoke in decades of riding, but the few I've seen break were on wheels which were insufficiently tensioned. It's never too much tension. That will pull a spoke through the rim, but won't cause it to break. It's always too little tension which causes the spoke to break through fatigue failure.

Yeah, I bet some LBS do see broken spokes all right. There are some LBS, people, and manufacturers out there who either don't know how or can't be bothered to put out a properly tensioned wheel. The facts outlined in the OP are totally explainable by the above. Let's call it a cluster. Sometimes there's a reason for a cluster other than random probability.