Dozens of different ways, I should think, but foremost among them is by example. If you mother only had the one child, or maybe two... you don't grow up to have seven yourself. But then they send young children to school where many or most of the teachers are childless women. Their television programming will portray most women as childless, and those without children as being the happiest, and so on. I don't know anything about Greek comedy entertainment, but if it's anything like that of the rest of the western world, there will be all those groaner jokes about how horrible having a family is.

There are other childless cultures where these aren't the major factors in childlessness, but Greece doesn't strike me as one of those.