Amagine what is will be if the person with fake diploma will became a doctor and start to treat people. He can kill the people insted of treatment.
In the same way, the same architect who bought a diploma can make a plan for such a house, which may collapse after settling. There will be a lot of grief.
Or pilot of the plane without dipmoma. It can cost not one human life. And there is not only deplomas, there are a lot of different sertificats from different refresher course and upgrades.