Debit/Credit cards no longer usable in dispensaries.....what the heck?

It's due to Drug Conspiracy laws:
"A drug conspiracy is an agreement to violate the narcotics laws. To convict a person of a drug conspiracy requires a prosecutor prove beyond a reasonable doubt that there was an agreement by two or more persons to distribute an illegal drug. The essence of a drug conspiracy crime is the agreement. A conviction for a drug conspiracy requires proof that:"

Exchanging cash does not provide proof. An electronic record of a deduction from your account directly to a business dealing solely with the sale of federally illegal narcotics will be enough to "prove" you had an agreement. The banks are most likely covering their own asses, otherwise, they would be the facilitators of said agreement, thus complicit in the agreement themselves, and thus part of the conspiracy to break narcotics laws.

Don't use your card, take 5 minutes to stop at an ATM, and always use cash. These records do not disappear (just like, essentially, everything on the internet). It can potentially come back to bite you in the ass 1, 5, 10+ years later.