@jwtownshend @letterluxe The long tradition in Massachusetts is to regulate or ban a thing first, and ask questions later. (This has had good and bad effects depending on the issue.)
According to this story, the ban only goes back to the early 1960s and might have been linked to New York's ban after a hepatitis outbreak. Personally, I remember older folks talking about the possibility of AIDS transmission back in the 1980s-1990s, but the ban was already in place then.
Interesting that tattooing wasn't legalized by the legislature here, but by an ACLU lawsuit.