Why have open lessons?

During this time of the year it is common for kindergartens to have open lessons so that parents can come and see their kids being taught. This would be good if parents of all kids could come. This is not always the case and often in those lessons you can see some kids crying because their parents did not come while the parents of the other kids came. Not all parents can attend these lessons even when they are in the late afternoon.

So why hold these. We as parents know through other means including from our kids that they are being taught and we can see them learn many things. To me all this does is interrupt the regular program and leaves some kids with the question “why didn’t mom or dad come to see me like the parents of other kids did?”.