This seems to be a real problem. The reason maybe the association of Port with the traditional consumption by the Portuguese immigrant community in France that focused on cheaper wines.
Besides France, on a global scale, Port Wine may be affected by its traditional use by the older generation, therefore associated with an « oldish » lifestyle.
If this is the case we could try to associate Port with more modern drinking patterns, such as Desert wine, fit to dark chocolate based deserts, etc.
Open for discussion, other ideas would be appreciated.
