Those carts are leathal.
My wife suffered injuries during an airpocket incident last year on an A310.
Her and the cart were eye level pinned to the celicing at the rear, could of been worse, she had a lucky landing well falling back to the floor.
As for seat belts, the only time i take mine off is for the toilet, but you hear so many unclick as soon as fasten seatbelt sign is turned off.