RequiredError message not shown when form is not using FieldFactory

When I placed a required TextField field in a Form that generates the field using a FieldFactory, the required error message is shown at the bottom of the form when the TextField is empty and the submit button is clicked.

But, when I placed a required TextField field in a Form directly (without using the FieldFactory), the required message is not shown when the field is empty and the submit button is clicked. Why is that?

Both TextField fields have the required asterisk * shown and the required message is shown in the tooltip when mouse over the field.

This is how my TextField is defined:

        TextField vendorTF = new TextField();
        vendorTF.setCaption("Vendor:");
        vendorTF.setRequired(true);
        vendorTF.setRequiredError("Vendor: required");
        vendorTF.setMaxLength(32);
        vendorTF.setNullRepresentation(""); 

Here is my button implementation:

public BottomLayout(final Form ipForm) {
setSpacing(true);

        Button bottomAddBTN;
        bottomAddBTN = new Button("Add", new Button.ClickListener() {
            @Override
            public void buttonClick(ClickEvent event) {
                try {
                    ipForm.commit();
                } 
                catch (Exception e) {
                    System.out.println("Add ERROR: " + e.toString());
                }
            }
        });

        Button bottomCancelBTN = new Button("Cancel", new Button.ClickListener() {
            @Override
            public void buttonClick(ClickEvent event) {
                try {
                    ipForm.discard();
                } 
                catch (Exception e) {
                    System.out.println("CANCEL ERROR: " + e.toString());
                }
            }
        });

        addComponent(bottomAddBTN);
        setComponentAlignment(bottomAddBTN, Alignment.BOTTOM_LEFT);
        addComponent(bottomCancelBTN);
        setComponentAlignment(bottomCancelBTN, Alignment.BOTTOM_LEFT);
    }

Any help in this would be greatly appreciated. Thank you!