It is to some. But it's not considered metropolitan enough to many. It's not that no banks will move there - clearly they will, there are plenty there aready. It's that Paris is a better brand for a large portion of employees. For staff with ties to London, it's also near-commutable. I've worked with people in London doing weekend-commuting far longer (in travel time) that Paris.
But most major banks have desks both in Frankfurt and Paris already, not just to handle local business but because it's hard enough getting top people to London (my ex even regularly tells me of her frustrations of dealing with offices in certain countries that exists solely because a single hotshot trader prefers a certain city over one of their big centres and brings in enough business for it to be worth a whole support staff to keep them happy) and so most of these banks needs presences in lots of places to be attractive.
If you don't have a presence in Paris and your competitor does, you're going to lose a sufficient portion of high-value traders to competitors over it for it to be an issue.
But most major banks have desks both in Frankfurt and Paris already, not just to handle local business but because it's hard enough getting top people to London (my ex even regularly tells me of her frustrations of dealing with offices in certain countries that exists solely because a single hotshot trader prefers a certain city over one of their big centres and brings in enough business for it to be worth a whole support staff to keep them happy) and so most of these banks needs presences in lots of places to be attractive.
If you don't have a presence in Paris and your competitor does, you're going to lose a sufficient portion of high-value traders to competitors over it for it to be an issue.