Perhaps that's because we have a strict guideline as to when we can and can't work? It's not very clever to fly when your sinuses are blocked or go to work when suffering from gastroenteritis as you are dealing with food.
The blocked sinuses and food handling excuses are often trotted out. The fact remains that pilots are subject to far more stringent health regulations, are required to take an annual medical check and must consult the CAA doctors when taking prescribed medication, something which often results in them being prevented from flying, yet they still take a fraction of the sick days that cabin crew do. The biggest problem in the cabin crew community is social sickness. I doubt it's coincidence that cabin crew sickness peaks around public holidays and popular social events. And before you say it, no, maternity absence is not counted as a sick day by BA.