No, hyphens cannot be opt-out. It has to be opt-in. This philosophical approach does not take into account future elements – each with their own UI requirements. What about selects? What about checkbox labels? Should they all have hyphens? What if there is a new User Interface for Tabs? We cannot be always on our toes to find out which next newly introduced browser feature will break our carefully laid out design.
Hyphens should only be used when the developer is sure there is going to be content and nothing else. Typically that would be a paragraph element, list element or similar.