Honestly that's just sampling bias. The current high profile crop are only from Navy pilots. But there's lots of data of unexplained things happening over other areas (Phoenix lights, Belgium wave, Mexico City UFOs). The difference now is that instead of random civilians, or other country militaries, saying they saw it and being ignored by the media mostly, the US armed services are pushing the story out there. None of that means that armed services are the only ones that have encountered this or have evidence of it. But the coordinated narrative, "authority source" and push definitely raises the prominence of these stories in relation to others.