When you have multiple buttons in a
VBox or a
HBox you often want to size and align them equally. The default preferred width of a button is computed based on its content (which includes the text as well as possible graphics) and the default preferred size of a
VBox and a
HBox is based on the biggest of their children.
If you want your buttons to grow with their parent you either have to raise their max size manually or to set it to the constant
Double.MAX_VALUE which forces controls to grow as big as permitted by their parent.