My theory: they taste like pine trees, and we've got a lot of pine trees, so it just feels right. Try drinking an IPA in Mexico sometimes. Super inappropes. But in PNW it makes sense. For awhile, til you get sick of it.
And Googling for "beer with pine needles"...
...dammit. "Spruce beer". That idea is literally centuries old. At least five breweries currently use evergreen bits as flavoring agents, and at least 16 have tried reviving gruit recipes in some form or another. Apparently, Sitka spruce tips are popular in Alaska, being far more available than hops.
(Personally, I wasn't a fan of IPAs before they got big, but preferred the amber -> porter/stout range)
I think theres also regional hop variations, so maybe theyre just less piney here.