Some int'l carriers (in premium cabins) don't seem to outwardly mind, or expressly state to use the call bell if I want something. I've even had a domestic US airline state the same when the FA says "I'm going to help them out in back - if you need something ..."

Meanwhile, given the apparent declining morale on my preferred airline, including getting an occasional snippy response when asking for something, or asking to remove dirty serviceware that has been sitting for an hour-plus, I'm getting "less shy" with the bell. I'd say I use it not more than a couple of times a year, but in a premium cabin service, sans emergency, it should never be necessary, but I'm finding that getting decent service is not as frequent as in the days of auld lang syne.