Consumers in non-grape wine producing provinces and that jurisdiction would benefit from helping to build a national wine industry that all Canadians could be proud of. Americans are proud of their wine industry; the French are proud of theirs.
If national pride isn't a good enough reason to do it, I would suggest another. If I go down to Rue Saint-Denis in Montreal, get myself a nice sports jacket, pay for the jacket, and leave revenue and taxes in Quebec, how has Ontario benefitted from that transaction? If you applied that logic, you could shut down the tourism industry in this country. You couldn't travel through this country and not leave some money where you were visiting. Wine is no different.