I tend NOT to question a Flight Crew on this issue.

Just because they get news of turbulence doesn't mean you'll have it on your flight and just because no other A/C reported it doesn't mean you won't be on the roller coaster.

back when the 321 had 26 F Seats we were going from BOS-PHL in absolute crap weather. The F/A in F was determined we should have cocktails. I had several!! Two on me and one in me. Yepper you read it right. She went airborne inside the plane and my seat mates and my Gin & Tonic landed on me. Second try was the charm and I got a nice drink.

Now I like a good Gin and Tonic as well as the next guy, but for her to risk injury so I can have one? Not interested. That dive lifeted her right into the headliner and dumped her in the aisle. Generally speaking if they are sitting there is a reason and laziness and their weight isn't it.

You're far more likely to see the laziness on the contract carriers although one has to wonder if US tacitly encourages no beverage service on short flights to save money?