We have the ability to call and tell them it's bumpy, or ask why it's on so long if it's smooth (99.9 percent of the time they forgot), but control? Not so much.
That leads to another interesting question: what's the proper etiquette for asking the captain to turn the seat belt sign off? It seems that leaving it on is a common occurrence, and for those sitting in Y, by the time the captain remembers, there's already a cart blocking the way.
Although I guess with the reduction in meal services, that won't be as much of an issue anymore...