There are many issues relating to ceilings and how draft proof they are. Age will be an important factor. Older homes that were built using plaster ceilings may find that they have deteriorated over time. This could be due to the natural materials like horsehair that they were made from, but it could also be from water leaking through the roof as a result of broken tiles. Over time, plaster ceilings can easily form fine small cracks, especially around decorative areas and where lights are secured.
More modern homes may fair better. However they still experience issues. It’s difficult to see if there are hidden gaps in the space between a light fitting and the ceiling. Tracer gas testing and blower door testing is ideal to locate the leaks in these areas. If your home has alarm sensors mounted on the roof, these are usually connected by cables throughout the house using holes in the ceiling, so they are another source of air leaks.