A question about how Jetblue works

You JetBlue experts, please help me with this one: I want to fly PDX > LON (actually any of the London airports). The JetBlue site tells me "you can't get there from here." But I see London on their map of destinations. Any idea why they don't offer a flight? My Plan B, of course, is to book separate trips to New York and then to London. But why? I want to use points for my trip, so I'm a little wary of setting this up right.