I think it all started with my first pregnancy and it just went down hill from there. I don't know why this happens, but it is a sad fact of motherhood. It must be some coordination brain cells giving up the ghost in the process of teaching our children to eat.
You either get food on you from your kids putting it there (throwing it at you, spitting it at you or throwing it up on you) by preparing or cleaning up meals (larger body parts being more likely to rub against the counter top) or just by being so darn tired or trying to multi task too many things at once that you just plain miss your mouth.
Oh to be young and have a clean shirt.