We know what causes that now. Usually this is a supposedly witty response to news of a pregnancy. It is a statement about cause and effect, not blame. The blame game involves making moral judgments about actions of free will.
There are times when those with free will exercise it according to their moral compasses. I don’t think we can be totally deterministic about the reasons behind human behavior. There will be consequences from these and any other actions taken by people. We reap what we sow.
The problem comes when we want to place blame outside the sequence of cause and effect. A little child may do so, blaming his/her parents’ fighting on his/her behavior, for instance. However, we ought to be able to grow up and move beyond this. A child may be excused for thinking that planting beans could yield an apple tree, but most of us should know better.
It is disturbing to me to hear politicians still playing such infantile blame games. A certain church has become famous for picketing funerals and other events, declaring that wars, accidents and other tragedies are the result of someone else who was not in the line of cause and effect at all. Non sequitur arguments abound in politics and pulpits as well. Usually it is a vulnerable population that is used as a scapegoat for the ills of society or natural disasters.
Sadly, this seems to be an integral part of some major faith traditions. One man and one woman ate forbidden fruit so death came to everything. A flood covered the earth because man was immoral. A whole valley with several cities was destroyed by fire and brimstone because some men in one city were immoral. Disasters come on many because of the sins of a few.
With these stories in our book of origins, it is no wonder that people seek someone to blame whenever great calamity strikes. It is hard enough to accept the consequences for our own poor choices, but we do not need to accept the blame for something we did not cause. I wonder when we will grow up as a society and move beyond the blame game.