They should have installed proper financial support for this business before legalizing the trade, but indeed maybe good news for Bitcoin. But still a hassle for the shopkeeper.
But that would mean changing federal laws.
I'm not from the US so I am not familiar with this state law - federal law system. I'm from the Netherlands where having weed in small amount is not illegal, buying is nor legal or illegal (grey area) but buying weed as a coffeeshop is illegal. This creates a backdoor system of supply to coffeeshops that comes with a lot of criminality. I believe in full legalization, with the laws to support or criminalization. Legalization has the benefit, tax income, less criminality, controllable quality of substance. (disclaimer: not a user myself)