For many many years I have cringed when politicians shake hands in crowds and hold other people’s babies. I thought maybe COVID would cure that practice, but doubtful.
As @jca2 said I think they wait for someone else to make the move first, but that can also be difficult, because when caught up in shaking a lot of hands then often times everyone is extending their hand at once and you can easily get caught up in the moment. Plus, it’s a habit hard to break when meeting people.