Taxpayers' money is being used to subsidise Savile Row rents in order to help preserve the street's heritage. It's a misguided political intervention that ignores a changing world.
While the maintenance of a local specialised work force may be integral to the bespoke suit business, that surely is up to the industry to ensure. But this seems to me more reminiscent of manufacturers of various items such as Parma ham, Bordeaux wine and Feta cheese seeking regulatory intervention to defend a competitive advantage. I can see some validity to this if the production location contributes to quality which, in the case of foodstuffs, may be true due to climate and ecology.
But, if it's just about the label, then what guarantee of quality is that? It hopes to make the customer think that by making suits physically in Savile Row (as opposed to utilising expertise that may once only have existed in that street) you are de facto superior to other suit makers. This may be true, but if you need subsidies to maintain that "tradition" it's not clear to me that it's defensible.
Nor is it wise for the producers because it skews the value equation and allows other people falsely to claim excellence solely on the basis of location. What is important is not the name but the name you make for yourself. Piggybacking may be fun but not if you're the one being ridden.