This isn’t just a westbound flight issue. I had this a few years ago on AA142, the daytime eastbound JFK-LHR flight.
AA142 JFK-LHR day flight shutters closed
I do wonder though, is this a particular problem with US carriers? My sense is that (and flak jacket at the ready, waiting to be pillioried) flight attendants on US carriers who work
transatlantic routes tend to be quite senior and eager not to work as hard as their younger colleagues might be, which might explain why the idea of a darkened cabin to encourage passengers to sleep is so appealing.