Some would say that good service is anticipating the needs of the customer.
Clearly it can be a personal preference - do you prefer the service where you just ring the call button when you need (often on CX F) and they come immediately, or where they're constantly marching up and down the aisles (SQ apparently)?
Or really - a balance?

I think in an ideal world they should ask, but that maybe becomes difficult with 36+ passengers. If I was hungry, and the menu said "dine on demand", then I would just demand.