Its just marketing...Banksy isn't just some anonymous street artist, its a well funded art studio. And they Banksy style itself was ripped a guerilla artist Blek le Rat...hence the use of Rats in Banksy works.

Society never really reacted to Blek Le Rat because he was a legit guerilla artist and as such his work remained unknown. Whereas the well funded art studio behind Banksy work mass marketed his art, it just so happens the marketing strategy was that of an anonymous street artist. Yet in reality his work was often shown and sold in galleries catering to the rich and celebrity types reinforcing its "value", now the studio even sells the work direct through auctions houses, it is anything but an organic reaction by society.