it might be a cultural thing too. I live near a heavily Latino neighborhood and in this neighborhood it is very common to see people wearing rosaries around their necks. I don’t see how this is much different than wearing a crucifix or medal around your neck. the only drawback is that it is hard to actually use the rosary to pray if you have it around your neck. But it certainly isn’t blasphemy. It only gets into blasphemy territory when the rosary is worn only as jewelry and with an unchaste outfit and behavior (think Madonna in the 80s - she wore rosaries and little else in her videos.)